qemu-system(1)

QEMU.1(1)QEMU.1(1)
NAME
qemu-doc - QEMU version 2.12.0 User Documentation
SYNOPSIS
qemu-system-i386 [options] [disk_image]
DESCRIPTION
The QEMU PC System emulator simulates the following peripherals:
- i440FX host PCI bridge and PIIX3 PCI to ISA bridge
- Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA
extensions (hardware level, including all non standard modes).
- PS/2 mouse and keyboard
- 2 PCI IDE interfaces with hard disk and CD-ROM support
- Floppy disk
- PCI and ISA network adapters
- Serial ports
- IPMI BMC, either and internal or external one
- Creative SoundBlaster 16 sound card
- ENSONIQ AudioPCI ES1370 sound card
- Intel 82801AA AC97 Audio compatible sound card
- Intel HD Audio Controller and HDA codec
- Adlib (OPL2) - Yamaha YM3812 compatible chip
- Gravis Ultrasound GF1 sound card
- CS4231A compatible sound card
- PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1
hub.
SMP is supported with up to 255 CPUs.
QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs
LGPL VGA BIOS.
QEMU uses YM3812 emulation by Tatsuyuki Satoh.
QEMU uses GUS emulation (GUSEMU32 <http://www.deinmeister.de/gusemu/>)
by Tibor "TS" Schutz.
Note that, by default, GUS shares IRQ(7) with parallel ports and so
QEMU must be told to not have parallel ports to have working GUS.
qemu-system-i386 dos.img -soundhw gus -parallel none
Alternatively:
qemu-system-i386 dos.img -device gus,irq=5
Or some other unclaimed IRQ.
CS4231A is the chip used in Windows Sound System and GUSMAX products
OPTIONS
disk_image is a raw hard disk image for IDE hard disk 0. Some targets
do not need a disk image.
Standard options
-h Display help and exit
-version
Display version information and exit
-machine [type=]name[,prop=value[,...]]
Select the emulated machine by name. Use "-machine help" to list
available machines.
For architectures which aim to support live migration compatibility
across releases, each release will introduce a new versioned
machine type. For example, the 2.8.0 release introduced machine
types "pc-i440fx-2.8" and "pc-q35-2.8" for the x86_64/i686
architectures.
To allow live migration of guests from QEMU version 2.8.0, to QEMU
version 2.9.0, the 2.9.0 version must support the "pc-i440fx-2.8"
and "pc-q35-2.8" machines too. To allow users live migrating VMs to
skip multiple intermediate releases when upgrading, new releases of
QEMU will support machine types from many previous versions.
Supported machine properties are:
accel=accels1[:accels2[:...]]
This is used to enable an accelerator. Depending on the target
architecture, kvm, xen, hax, hvf, whpx or tcg can be available.
By default, tcg is used. If there is more than one accelerator
specified, the next one is used if the previous one fails to
initialize.
kernel_irqchip=on|off
Controls in-kernel irqchip support for the chosen accelerator
when available.
gfx_passthru=on|off
Enables IGD GFX passthrough support for the chosen machine when
available.
vmport=on|off|auto
Enables emulation of VMWare IO port, for vmmouse etc. auto says
to select the value based on accel. For accel=xen the default
is off otherwise the default is on.
kvm_shadow_mem=size
Defines the size of the KVM shadow MMU.
dump-guest-core=on|off
Include guest memory in a core dump. The default is on.
mem-merge=on|off
Enables or disables memory merge support. This feature, when
supported by the host, de-duplicates identical memory pages
among VMs instances (enabled by default).
aes-key-wrap=on|off
Enables or disables AES key wrapping support on s390-ccw hosts.
This feature controls whether AES wrapping keys will be created
to allow execution of AES cryptographic functions. The default
is on.
dea-key-wrap=on|off
Enables or disables DEA key wrapping support on s390-ccw hosts.
This feature controls whether DEA wrapping keys will be created
to allow execution of DEA cryptographic functions. The default
is on.
nvdimm=on|off
Enables or disables NVDIMM support. The default is off.
s390-squash-mcss=on|off
Enables or disables squashing subchannels into the default css.
The default is off. NOTE: This property is deprecated and will
be removed in future releases. The "s390-squash-mcss=on"
property has been obsoleted by allowing the cssid to be chosen
freely. Instead of squashing subchannels into the default
channel subsystem image for guests that do not support multiple
channel subsystems, all devices can be put into the default
channel subsystem image.
enforce-config-section=on|off
If enforce-config-section is set to on, force migration code to
send configuration section even if the machine-type sets the
migration.send-configuration property to off. NOTE: this
parameter is deprecated. Please use -global
migration.send-configuration=on|off instead.
memory-encryption=
Memory encryption object to use. The default is none.
-cpu model
Select CPU model ("-cpu help" for list and additional feature
selection)
-accel name[,prop=value[,...]]
This is used to enable an accelerator. Depending on the target
architecture, kvm, xen, hax, hvf, whpx or tcg can be available. By
default, tcg is used. If there is more than one accelerator
specified, the next one is used if the previous one fails to
initialize.
thread=single|multi
Controls number of TCG threads. When the TCG is multi-threaded
there will be one thread per vCPU therefor taking advantage of
additional host cores. The default is to enable multi-threading
where both the back-end and front-ends support it and no
incompatible TCG features have been enabled (e.g.
icount/replay).
-smp
[cpus=]n[,cores=cores][,threads=threads][,sockets=sockets][,maxcpus=maxcpus]
Simulate an SMP system with n CPUs. On the PC target, up to 255
CPUs are supported. On Sparc32 target, Linux limits the number of
usable CPUs to 4. For the PC target, the number of cores per
socket, the number of threads per cores and the total number of
sockets can be specified. Missing values will be computed. If any
on the three values is given, the total number of CPUs n can be
omitted. maxcpus specifies the maximum number of hotpluggable CPUs.
-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node]
-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node]
-numa dist,src=source,dst=destination,val=distance
-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]
Define a NUMA node and assign RAM and VCPUs to it. Set the NUMA
distance from a source node to a destination node.
Legacy VCPU assignment uses cpus option where firstcpu and lastcpu
are CPU indexes. Each cpus option represent a contiguous range of
CPU indexes (or a single VCPU if lastcpu is omitted). A non-
contiguous set of VCPUs can be represented by providing multiple
cpus options. If cpus is omitted on all nodes, VCPUs are
automatically split between them.
For example, the following option assigns VCPUs 0, 1, 2 and 5 to a
NUMA node:
-numa node,cpus=0-2,cpus=5
cpu option is a new alternative to cpus option which uses
socket-id|core-id|thread-id properties to assign CPU objects to a
node using topology layout properties of CPU. The set of
properties is machine specific, and depends on used machine
type/smp options. It could be queried with hotpluggable-cpus
monitor command. node-id property specifies node to which CPU
object will be assigned, it's required for node to be declared with
node option before it's used with cpu option.
For example:
-M pc \
-smp 1,sockets=2,maxcpus=2 \
-numa node,nodeid=0 -numa node,nodeid=1 \
-numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1
mem assigns a given RAM amount to a node. memdev assigns RAM from a
given memory backend device to a node. If mem and memdev are
omitted in all nodes, RAM is split equally between them.
mem and memdev are mutually exclusive. Furthermore, if one node
uses memdev, all of them have to use it.
source and destination are NUMA node IDs. distance is the NUMA
distance from source to destination. The distance from a node to
itself is always 10. If any pair of nodes is given a distance, then
all pairs must be given distances. Although, when distances are
only given in one direction for each pair of nodes, then the
distances in the opposite directions are assumed to be the same.
If, however, an asymmetrical pair of distances is given for even
one node pair, then all node pairs must be provided distance values
for both directions, even when they are symmetrical. When a node is
unreachable from another node, set the pair's distance to 255.
Note that the -numa option doesn't allocate any of the specified
resources, it just assigns existing resources to NUMA nodes. This
means that one still has to use the -m, -smp options to allocate
RAM and VCPUs respectively.
-add-fd fd=fd,set=set[,opaque=opaque]
Add a file descriptor to an fd set. Valid options are:
fd=fd
This option defines the file descriptor of which a duplicate is
added to fd set. The file descriptor cannot be stdin, stdout,
or stderr.
set=set
This option defines the ID of the fd set to add the file
descriptor to.
opaque=opaque
This option defines a free-form string that can be used to
describe fd.
You can open an image using pre-opened file descriptors from an fd
set:
qemu-system-i386
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk
-set group.id.arg=value
Set parameter arg for item id of type group
-global driver.prop=value
-global driver=driver,property=property,value=value
Set default value of driver's property prop to value, e.g.:
qemu-system-i386 -global ide-hd.physical_block_size=4096 disk-image.img
In particular, you can use this to set driver properties for
devices which are created automatically by the machine model. To
create a device which is not created automatically and set
properties on it, use -device.
-global driver.prop=value is shorthand for -global
driver=driver,property=prop,value=value. The longhand syntax works
even when driver contains a dot.
-boot
[order=drives][,once=drives][,menu=on|off][,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_timeout][,strict=on|off]
Specify boot order drives as a string of drive letters. Valid drive
letters depend on the target architecture. The x86 PC uses: a, b
(floppy 1 and 2), c (first hard disk), d (first CD-ROM), n-p
(Etherboot from network adapter 1-4), hard disk boot is the
default. To apply a particular boot order only on the first
startup, specify it via once. Note that the order or once parameter
should not be used together with the bootindex property of devices,
since the firmware implementations normally do not support both at
the same time.
Interactive boot menus/prompts can be enabled via menu=on as far as
firmware/BIOS supports them. The default is non-interactive boot.
A splash picture could be passed to bios, enabling user to show it
as logo, when option splash=sp_name is given and menu=on, If
firmware/BIOS supports them. Currently Seabios for X86 system
support it. limitation: The splash file could be a jpeg file or a
BMP file in 24 BPP format(true color). The resolution should be
supported by the SVGA mode, so the recommended is 320x240, 640x480,
800x640.
A timeout could be passed to bios, guest will pause for rb_timeout
ms when boot failed, then reboot. If rb_timeout is '-1', guest will
not reboot, qemu passes '-1' to bios by default. Currently Seabios
for X86 system support it.
Do strict boot via strict=on as far as firmware/BIOS supports it.
This only effects when boot priority is changed by bootindex
options. The default is non-strict boot.
# try to boot from network first, then from hard disk
qemu-system-i386 -boot order=nc
# boot from CD-ROM first, switch back to default order after reboot
qemu-system-i386 -boot once=d
# boot with a splash picture for 5 seconds.
qemu-system-i386 -boot menu=on,splash=/root/boot.bmp,splash-time=5000
Note: The legacy format '-boot drives' is still supported but its
use is discouraged as it may be removed from future versions.
-m [size=]megs[,slots=n,maxmem=size]
Sets guest startup RAM size to megs megabytes. Default is 128 MiB.
Optionally, a suffix of "M" or "G" can be used to signify a value
in megabytes or gigabytes respectively. Optional pair slots, maxmem
could be used to set amount of hotpluggable memory slots and
maximum amount of memory. Note that maxmem must be aligned to the
page size.
For example, the following command-line sets the guest startup RAM
size to 1GB, creates 3 slots to hotplug additional memory and sets
the maximum memory the guest can reach to 4GB:
qemu-system-x86_64 -m 1G,slots=3,maxmem=4G
If slots and maxmem are not specified, memory hotplug won't be
enabled and the guest startup RAM will never increase.
-mem-path path
Allocate guest RAM from a temporarily created file in path.
-mem-prealloc
Preallocate memory when using -mem-path.
-k language
Use keyboard layout language (for example "fr" for French). This
option is only needed where it is not easy to get raw PC keycodes
(e.g. on Macs, with some X11 servers or with a VNC or curses
display). You don't normally need to use it on PC/Linux or
PC/Windows hosts.
The available layouts are:
ar de-ch es fo fr-ca hu ja mk no pt-br sv
da en-gb et fr fr-ch is lt nl pl ru th
de en-us fi fr-be hr it lv nl-be pt sl tr
The default is "en-us".
-audio-help
Will show the audio subsystem help: list of drivers, tunable
parameters.
-soundhw card1[,card2,...] or -soundhw all
Enable audio and selected sound hardware. Use 'help' to print all
available sound hardware.
qemu-system-i386 -soundhw sb16,adlib disk.img
qemu-system-i386 -soundhw es1370 disk.img
qemu-system-i386 -soundhw ac97 disk.img
qemu-system-i386 -soundhw hda disk.img
qemu-system-i386 -soundhw all disk.img
qemu-system-i386 -soundhw help
Note that Linux's i810_audio OSS kernel (for AC97) module might
require manually specifying clocking.
modprobe i810_audio clocking=48000
-balloon virtio[,addr=addr]
Enable virtio balloon device, optionally with PCI address addr.
This option is deprecated, use --device virtio-balloon instead.
-device driver[,prop[=value][,...]]
Add device driver. prop=value sets driver properties. Valid
properties depend on the driver. To get help on possible drivers
and properties, use "-device help" and "-device driver,help".
Some drivers are:
-device
ipmi-bmc-sim,id=id[,slave_addr=val][,sdrfile=file][,furareasize=val][,furdatafile=file]
Add an IPMI BMC. This is a simulation of a hardware management
interface processor that normally sits on a system. It provides a
watchdog and the ability to reset and power control the system.
You need to connect this to an IPMI interface to make it useful
The IPMI slave address to use for the BMC. The default is 0x20.
This address is the BMC's address on the I2C network of management
controllers. If you don't know what this means, it is safe to
ignore it.
bmc=id
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern
above.
slave_addr=val
Define slave address to use for the BMC. The default is 0x20.
sdrfile=file
file containing raw Sensor Data Records (SDR) data. The default
is none.
fruareasize=val
size of a Field Replaceable Unit (FRU) area. The default is
1024.
frudatafile=file
file containing raw Field Replaceable Unit (FRU) inventory
data. The default is none.
-device ipmi-bmc-extern,id=id,chardev=id[,slave_addr=val]
Add a connection to an external IPMI BMC simulator. Instead of
locally emulating the BMC like the above item, instead connect to
an external entity that provides the IPMI services.
A connection is made to an external BMC simulator. If you do this,
it is strongly recommended that you use the "reconnect=" chardev
option to reconnect to the simulator if the connection is lost.
Note that if this is not used carefully, it can be a security
issue, as the interface has the ability to send resets, NMIs, and
power off the VM. It's best if QEMU makes a connection to an
external simulator running on a secure port on localhost, so
neither the simulator nor QEMU is exposed to any outside network.
See the "lanserv/README.vm" file in the OpenIPMI library for more
details on the external interface.
-device isa-ipmi-kcs,bmc=id[,ioport=val][,irq=val]
Add a KCS IPMI interafce on the ISA bus. This also adds a
corresponding ACPI and SMBIOS entries, if appropriate.
bmc=id
The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern
above.
ioport=val
Define the I/O address of the interface. The default is 0xca0
for KCS.
irq=val
Define the interrupt to use. The default is 5. To disable
interrupts, set this to 0.
-device isa-ipmi-bt,bmc=id[,ioport=val][,irq=val]
Like the KCS interface, but defines a BT interface. The default
port is 0xe4 and the default interrupt is 5.
-name name
Sets the name of the guest. This name will be displayed in the SDL
window caption. The name will also be used for the VNC server.
Also optionally set the top visible process name in Linux. Naming
of individual threads can also be enabled on Linux to aid
debugging.
-uuid uuid
Set system UUID.
Block device options
-fda file
-fdb file
Use file as floppy disk 0/1 image.
-hda file
-hdb file
-hdc file
-hdd file
Use file as hard disk 0, 1, 2 or 3 image.
-cdrom file
Use file as CD-ROM image (you cannot use -hdc and -cdrom at the
same time). You can use the host CD-ROM by using /dev/cdrom as
filename.
-blockdev option[,option[,option[,...]]]
Define a new block driver node. Some of the options apply to all
block drivers, other options are only accepted for a specific block
driver. See below for a list of generic options and options for the
most common block drivers.
Options that expect a reference to another node (e.g. "file") can
be given in two ways. Either you specify the node name of an
already existing node (file=node-name), or you define a new node
inline, adding options for the referenced node after a dot
(file.filename=path,file.aio=native).
A block driver node created with -blockdev can be used for a guest
device by specifying its node name for the "drive" property in a
-device argument that defines a block device.
Valid options for any block driver node:
"driver"
Specifies the block driver to use for the given node.
"node-name"
This defines the name of the block driver node by which it
will be referenced later. The name must be unique, i.e. it
must not match the name of a different block driver node,
or (if you use -drive as well) the ID of a drive.
If no node name is specified, it is automatically
generated. The generated node name is not intended to be
predictable and changes between QEMU invocations. For the
top level, an explicit node name must be specified.
"read-only"
Open the node read-only. Guest write attempts will fail.
"cache.direct"
The host page cache can be avoided with cache.direct=on.
This will attempt to do disk IO directly to the guest's
memory. QEMU may still perform an internal copy of the
data.
"cache.no-flush"
In case you don't care about data integrity over host
failures, you can use cache.no-flush=on. This option tells
QEMU that it never needs to write any data to the disk but
can instead keep things in cache. If anything goes wrong,
like your host losing power, the disk storage getting
disconnected accidentally, etc. your image will most
probably be rendered unusable.
"discard=discard"
discard is one of "ignore" (or "off") or "unmap" (or "on")
and controls whether "discard" (also known as "trim" or
"unmap") requests are ignored or passed to the filesystem.
Some machine types may not support discard requests.
"detect-zeroes=detect-zeroes"
detect-zeroes is "off", "on" or "unmap" and enables the
automatic conversion of plain zero writes by the OS to
driver specific optimized zero write commands. You may even
choose "unmap" if discard is set to "unmap" to allow a zero
write to be converted to an "unmap" operation.
Driver-specific options for "file"
This is the protocol-level block driver for accessing regular
files.
"filename"
The path to the image file in the local filesystem
"aio"
Specifies the AIO backend (threads/native, default:
threads)
"locking"
Specifies whether the image file is protected with Linux
OFD / POSIX locks. The default is to use the Linux Open
File Descriptor API if available, otherwise no lock is
applied. (auto/on/off, default: auto)
Example:
-blockdev driver=file,node-name=disk,filename=disk.img
Driver-specific options for "raw"
This is the image format block driver for raw images. It is
usually stacked on top of a protocol level block driver such as
"file".
"file"
Reference to or definition of the data source block driver
node (e.g. a "file" driver node)
Example 1:
-blockdev driver=file,node-name=disk_file,filename=disk.img
-blockdev driver=raw,node-name=disk,file=disk_file
Example 2:
-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img
Driver-specific options for "qcow2"
This is the image format block driver for qcow2 images. It is
usually stacked on top of a protocol level block driver such as
"file".
"file"
Reference to or definition of the data source block driver
node (e.g. a "file" driver node)
"backing"
Reference to or definition of the backing file block device
(default is taken from the image file). It is allowed to
pass "null" here in order to disable the default backing
file.
"lazy-refcounts"
Whether to enable the lazy refcounts feature (on/off;
default is taken from the image file)
"cache-size"
The maximum total size of the L2 table and refcount block
caches in bytes (default: 1048576 bytes or 8 clusters,
whichever is larger)
"l2-cache-size"
The maximum size of the L2 table cache in bytes (default:
4/5 of the total cache size)
"refcount-cache-size"
The maximum size of the refcount block cache in bytes
(default: 1/5 of the total cache size)
"cache-clean-interval"
Clean unused entries in the L2 and refcount caches. The
interval is in seconds. The default value is 0 and it
disables this feature.
"pass-discard-request"
Whether discard requests to the qcow2 device should be
forwarded to the data source (on/off; default: on if
discard=unmap is specified, off otherwise)
"pass-discard-snapshot"
Whether discard requests for the data source should be
issued when a snapshot operation (e.g. deleting a snapshot)
frees clusters in the qcow2 file (on/off; default: on)
"pass-discard-other"
Whether discard requests for the data source should be
issued on other occasions where a cluster gets freed
(on/off; default: off)
"overlap-check"
Which overlap checks to perform for writes to the image
(none/constant/cached/all; default: cached). For details or
finer granularity control refer to the QAPI documentation
of "blockdev-add".
Example 1:
-blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2
-blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216
Example 2:
-blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2
Driver-specific options for other drivers
Please refer to the QAPI documentation of the "blockdev-add"
QMP command.
-drive option[,option[,option[,...]]]
Define a new drive. This includes creating a block driver node (the
backend) as well as a guest device, and is mostly a shortcut for
defining the corresponding -blockdev and -device options.
-drive accepts all options that are accepted by -blockdev. In
addition, it knows the following options:
file=file
This option defines which disk image to use with this drive. If
the filename contains comma, you must double it (for instance,
"file=my,,file" to use file "my,file").
Special files such as iSCSI devices can be specified using
protocol specific URLs. See the section for "Device URL Syntax"
for more information.
if=interface
This option defines on which type on interface the drive is
connected. Available types are: ide, scsi, sd, mtd, floppy,
pflash, virtio, none.
bus=bus,unit=unit
These options define where is connected the drive by defining
the bus number and the unit id.
index=index
This option defines where is connected the drive by using an
index in the list of available connectors of a given interface
type.
media=media
This option defines the type of the media: disk or cdrom.
cyls=c,heads=h,secs=s[,trans=t]
Force disk physical geometry and the optional BIOS translation
(trans=none or lba). These parameters are deprecated, use the
corresponding parameters of "-device" instead.
snapshot=snapshot
snapshot is "on" or "off" and controls snapshot mode for the
given drive (see -snapshot).
cache=cache
cache is "none", "writeback", "unsafe", "directsync" or
"writethrough" and controls how the host cache is used to
access block data. This is a shortcut that sets the
cache.direct and cache.no-flush options (as in -blockdev), and
additionally cache.writeback, which provides a default for the
write-cache option of block guest devices (as in -device). The
modes correspond to the following settings:
| cache.writeback cache.direct cache.no-flush
writeback | on off off
none | on on off
writethrough | off off off
directsync | off on off
unsafe | on off on
The default mode is cache=writeback.
aio=aio
aio is "threads", or "native" and selects between pthread based
disk I/O and native Linux AIO.
format=format
Specify which disk format will be used rather than detecting
the format. Can be used to specify format=raw to avoid
interpreting an untrusted format header.
serial=serial
This option specifies the serial number to assign to the
device. This parameter is deprecated, use the corresponding
parameter of "-device" instead.
addr=addr
Specify the controller's PCI address (if=virtio only). This
parameter is deprecated, use the corresponding parameter of
"-device" instead.
werror=action,rerror=action
Specify which action to take on write and read errors. Valid
actions are: "ignore" (ignore the error and try to continue),
"stop" (pause QEMU), "report" (report the error to the guest),
"enospc" (pause QEMU only if the host disk is full; report the
error to the guest otherwise). The default setting is
werror=enospc and rerror=report.
copy-on-read=copy-on-read
copy-on-read is "on" or "off" and enables whether to copy read
backing file sectors into the image file.
bps=b,bps_rd=r,bps_wr=w
Specify bandwidth throttling limits in bytes per second, either
for all request types or for reads or writes only. Small
values can lead to timeouts or hangs inside the guest. A safe
minimum for disks is 2 MB/s.
bps_max=bm,bps_rd_max=rm,bps_wr_max=wm
Specify bursts in bytes per second, either for all request
types or for reads or writes only. Bursts allow the guest I/O
to spike above the limit temporarily.
iops=i,iops_rd=r,iops_wr=w
Specify request rate limits in requests per second, either for
all request types or for reads or writes only.
iops_max=bm,iops_rd_max=rm,iops_wr_max=wm
Specify bursts in requests per second, either for all request
types or for reads or writes only. Bursts allow the guest I/O
to spike above the limit temporarily.
iops_size=is
Let every is bytes of a request count as a new request for iops
throttling purposes. Use this option to prevent guests from
circumventing iops limits by sending fewer but larger requests.
group=g
Join a throttling quota group with given name g. All drives
that are members of the same group are accounted for together.
Use this option to prevent guests from circumventing throttling
limits by using many small disks instead of a single larger
disk.
By default, the cache.writeback=on mode is used. It will report
data writes as completed as soon as the data is present in the host
page cache. This is safe as long as your guest OS makes sure to
correctly flush disk caches where needed. If your guest OS does not
handle volatile disk write caches correctly and your host crashes
or loses power, then the guest may experience data corruption.
For such guests, you should consider using cache.writeback=off.
This means that the host page cache will be used to read and write
data, but write notification will be sent to the guest only after
QEMU has made sure to flush each write to the disk. Be aware that
this has a major impact on performance.
When using the -snapshot option, unsafe caching is always used.
Copy-on-read avoids accessing the same backing file sectors
repeatedly and is useful when the backing file is over a slow
network. By default copy-on-read is off.
Instead of -cdrom you can use:
qemu-system-i386 -drive file=file,index=2,media=cdrom
Instead of -hda, -hdb, -hdc, -hdd, you can use:
qemu-system-i386 -drive file=file,index=0,media=disk
qemu-system-i386 -drive file=file,index=1,media=disk
qemu-system-i386 -drive file=file,index=2,media=disk
qemu-system-i386 -drive file=file,index=3,media=disk
You can open an image using pre-opened file descriptors from an fd
set:
qemu-system-i386
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk
You can connect a CDROM to the slave of ide0:
qemu-system-i386 -drive file=file,if=ide,index=1,media=cdrom
If you don't specify the "file=" argument, you define an empty
drive:
qemu-system-i386 -drive if=ide,index=1,media=cdrom
Instead of -fda, -fdb, you can use:
qemu-system-i386 -drive file=file,index=0,if=floppy
qemu-system-i386 -drive file=file,index=1,if=floppy
By default, interface is "ide" and index is automatically
incremented:
qemu-system-i386 -drive file=a -drive file=b"
is interpreted like:
qemu-system-i386 -hda a -hdb b
-mtdblock file
Use file as on-board Flash memory image.
-sd file
Use file as SecureDigital card image.
-pflash file
Use file as a parallel flash image.
-snapshot
Write to temporary files instead of disk image files. In this case,
the raw disk image you use is not written back. You can however
force the write back by pressing C-a s.
-fsdev
fsdriver,id=id,path=path,[security_model=security_model][,writeout=writeout][,readonly][,socket=socket|sock_fd=sock_fd][,fmode=fmode][,dmode=dmode]
Define a new file system device. Valid options are:
fsdriver
This option specifies the fs driver backend to use. Currently
"local", "handle" and "proxy" file system drivers are
supported.
id=id
Specifies identifier for this device
path=path
Specifies the export path for the file system device. Files
under this path will be available to the 9p client on the
guest.
security_model=security_model
Specifies the security model to be used for this export path.
Supported security models are "passthrough", "mapped-xattr",
"mapped-file" and "none". In "passthrough" security model,
files are stored using the same credentials as they are created
on the guest. This requires QEMU to run as root. In "mapped-
xattr" security model, some of the file attributes like uid,
gid, mode bits and link target are stored as file attributes.
For "mapped-file" these attributes are stored in the hidden
.virtfs_metadata directory. Directories exported by this
security model cannot interact with other unix tools. "none"
security model is same as passthrough except the sever won't
report failures if it fails to set file attributes like
ownership. Security model is mandatory only for local fsdriver.
Other fsdrivers (like handle, proxy) don't take security model
as a parameter.
writeout=writeout
This is an optional argument. The only supported value is
"immediate". This means that host page cache will be used to
read and write data but write notification will be sent to the
guest only when the data has been reported as written by the
storage subsystem.
readonly
Enables exporting 9p share as a readonly mount for guests. By
default read-write access is given.
socket=socket
Enables proxy filesystem driver to use passed socket file for
communicating with virtfs-proxy-helper
sock_fd=sock_fd
Enables proxy filesystem driver to use passed socket descriptor
for communicating with virtfs-proxy-helper. Usually a helper
like libvirt will create socketpair and pass one of the fds as
sock_fd
fmode=fmode
Specifies the default mode for newly created files on the host.
Works only with security models "mapped-xattr" and "mapped-
file".
dmode=dmode
Specifies the default mode for newly created directories on the
host. Works only with security models "mapped-xattr" and
"mapped-file".
-fsdev option is used along with -device driver "virtio-9p-pci".
-device virtio-9p-pci,fsdev=id,mount_tag=mount_tag
Options for virtio-9p-pci driver are:
fsdev=id
Specifies the id value specified along with -fsdev option
mount_tag=mount_tag
Specifies the tag name to be used by the guest to mount this
export point
-virtfs
fsdriver[,path=path],mount_tag=mount_tag[,security_model=security_model][,writeout=writeout][,readonly][,socket=socket|sock_fd=sock_fd][,fmode=fmode][,dmode=dmode]
The general form of a Virtual File system pass-through options are:
fsdriver
This option specifies the fs driver backend to use. Currently
"local", "handle" and "proxy" file system drivers are
supported.
id=id
Specifies identifier for this device
path=path
Specifies the export path for the file system device. Files
under this path will be available to the 9p client on the
guest.
security_model=security_model
Specifies the security model to be used for this export path.
Supported security models are "passthrough", "mapped-xattr",
"mapped-file" and "none". In "passthrough" security model,
files are stored using the same credentials as they are created
on the guest. This requires QEMU to run as root. In "mapped-
xattr" security model, some of the file attributes like uid,
gid, mode bits and link target are stored as file attributes.
For "mapped-file" these attributes are stored in the hidden
.virtfs_metadata directory. Directories exported by this
security model cannot interact with other unix tools. "none"
security model is same as passthrough except the sever won't
report failures if it fails to set file attributes like
ownership. Security model is mandatory only for local fsdriver.
Other fsdrivers (like handle, proxy) don't take security model
as a parameter.
writeout=writeout
This is an optional argument. The only supported value is
"immediate". This means that host page cache will be used to
read and write data but write notification will be sent to the
guest only when the data has been reported as written by the
storage subsystem.
readonly
Enables exporting 9p share as a readonly mount for guests. By
default read-write access is given.
socket=socket
Enables proxy filesystem driver to use passed socket file for
communicating with virtfs-proxy-helper. Usually a helper like
libvirt will create socketpair and pass one of the fds as
sock_fd
sock_fd
Enables proxy filesystem driver to use passed 'sock_fd' as the
socket descriptor for interfacing with virtfs-proxy-helper
fmode=fmode
Specifies the default mode for newly created files on the host.
Works only with security models "mapped-xattr" and "mapped-
file".
dmode=dmode
Specifies the default mode for newly created directories on the
host. Works only with security models "mapped-xattr" and
"mapped-file".
-virtfs_synth
Create synthetic file system image
-iscsi
Configure iSCSI session parameters.
USB options
-usb
Enable the USB driver (if it is not used by default yet).
-usbdevice devname
Add the USB device devname. Note that this option is deprecated,
please use "-device usb-..." instead.
mouse
Virtual Mouse. This will override the PS/2 mouse emulation when
activated.
tablet
Pointer device that uses absolute coordinates (like a
touchscreen). This means QEMU is able to report the mouse
position without having to grab the mouse. Also overrides the
PS/2 mouse emulation when activated.
braille
Braille device. This will use BrlAPI to display the braille
output on a real or fake device.
Display options
-display type
Select type of display to use. This option is a replacement for the
old style -sdl/-curses/... options. Valid values for type are
sdl Display video output via SDL (usually in a separate graphics
window; see the SDL documentation for other possibilities).
curses
Display video output via curses. For graphics device models
which support a text mode, QEMU can display this output using a
curses/ncurses interface. Nothing is displayed when the
graphics device is in graphical mode or if the graphics device
does not support a text mode. Generally only the VGA device
models support text mode.
none
Do not display video output. The guest will still see an
emulated graphics card, but its output will not be displayed to
the QEMU user. This option differs from the -nographic option
in that it only affects what is done with video output;
-nographic also changes the destination of the serial and
parallel port data.
gtk Display video output in a GTK window. This interface provides
drop-down menus and other UI elements to configure and control
the VM during runtime.
vnc Start a VNC server on display <arg>
-nographic
Normally, if QEMU is compiled with graphical window support, it
displays output such as guest graphics, guest console, and the QEMU
monitor in a window. With this option, you can totally disable
graphical output so that QEMU is a simple command line application.
The emulated serial port is redirected on the console and muxed
with the monitor (unless redirected elsewhere explicitly).
Therefore, you can still use QEMU to debug a Linux kernel with a
serial console. Use C-a h for help on switching between the console
and monitor.
-curses
Normally, if QEMU is compiled with graphical window support, it
displays output such as guest graphics, guest console, and the QEMU
monitor in a window. With this option, QEMU can display the VGA
output when in text mode using a curses/ncurses interface. Nothing
is displayed in graphical mode.
-no-frame
Do not use decorations for SDL windows and start them using the
whole available screen space. This makes the using QEMU in a
dedicated desktop workspace more convenient.
-alt-grab
Use Ctrl-Alt-Shift to grab mouse (instead of Ctrl-Alt). Note that
this also affects the special keys (for fullscreen, monitor-mode
switching, etc).
-ctrl-grab
Use Right-Ctrl to grab mouse (instead of Ctrl-Alt). Note that this
also affects the special keys (for fullscreen, monitor-mode
switching, etc).
-no-quit
Disable SDL window close capability.
-sdl
Enable SDL.
-spice option[,option[,...]]
Enable the spice remote desktop protocol. Valid options are
port=<nr>
Set the TCP port spice is listening on for plaintext channels.
addr=<addr>
Set the IP address spice is listening on. Default is any
address.
ipv4
ipv6
unix
Force using the specified IP version.
password=<secret>
Set the password you need to authenticate.
sasl
Require that the client use SASL to authenticate with the
spice. The exact choice of authentication method used is
controlled from the system / user's SASL configuration file for
the 'qemu' service. This is typically found in
/etc/sasl2/qemu.conf. If running QEMU as an unprivileged user,
an environment variable SASL_CONF_PATH can be used to make it
search alternate locations for the service config. While some
SASL auth methods can also provide data encryption (eg GSSAPI),
it is recommended that SASL always be combined with the 'tls'
and 'x509' settings to enable use of SSL and server
certificates. This ensures a data encryption preventing
compromise of authentication credentials.
disable-ticketing
Allow client connects without authentication.
disable-copy-paste
Disable copy paste between the client and the guest.
disable-agent-file-xfer
Disable spice-vdagent based file-xfer between the client and
the guest.
tls-port=<nr>
Set the TCP port spice is listening on for encrypted channels.
x509-dir=<dir>
Set the x509 file directory. Expects same filenames as -vnc
$display,x509=$dir
x509-key-file=<file>
x509-key-password=<file>
x509-cert-file=<file>
x509-cacert-file=<file>
x509-dh-key-file=<file>
The x509 file names can also be configured individually.
tls-ciphers=<list>
Specify which ciphers to use.
tls-channel=[main|display|cursor|inputs|record|playback]
plaintext-channel=[main|display|cursor|inputs|record|playback]
Force specific channel to be used with or without TLS
encryption. The options can be specified multiple times to
configure multiple channels. The special name "default" can be
used to set the default mode. For channels which are not
explicitly forced into one mode the spice client is allowed to
pick tls/plaintext as he pleases.
image-compression=[auto_glz|auto_lz|quic|glz|lz|off]
Configure image compression (lossless). Default is auto_glz.
jpeg-wan-compression=[auto|never|always]
zlib-glz-wan-compression=[auto|never|always]
Configure wan image compression (lossy for slow links).
Default is auto.
streaming-video=[off|all|filter]
Configure video stream detection. Default is off.
agent-mouse=[on|off]
Enable/disable passing mouse events via vdagent. Default is
on.
playback-compression=[on|off]
Enable/disable audio stream compression (using celt 0.5.1).
Default is on.
seamless-migration=[on|off]
Enable/disable spice seamless migration. Default is off.
gl=[on|off]
Enable/disable OpenGL context. Default is off.
rendernode=<file>
DRM render node for OpenGL rendering. If not specified, it will
pick the first available. (Since 2.9)
-portrait
Rotate graphical output 90 deg left (only PXA LCD).
-rotate deg
Rotate graphical output some deg left (only PXA LCD).
-vga type
Select type of VGA card to emulate. Valid values for type are
cirrus
Cirrus Logic GD5446 Video card. All Windows versions starting
from Windows 95 should recognize and use this graphic card. For
optimal performances, use 16 bit color depth in the guest and
the host OS. (This card was the default before QEMU 2.2)
std Standard VGA card with Bochs VBE extensions. If your guest OS
supports the VESA 2.0 VBE extensions (e.g. Windows XP) and if
you want to use high resolution modes (>= 1280x1024x16) then
you should use this option. (This card is the default since
QEMU 2.2)
vmware
VMWare SVGA-II compatible adapter. Use it if you have
sufficiently recent XFree86/XOrg server or Windows guest with a
driver for this card.
qxl QXL paravirtual graphic card. It is VGA compatible (including
VESA 2.0 VBE support). Works best with qxl guest drivers
installed though. Recommended choice when using the spice
protocol.
tcx (sun4m only) Sun TCX framebuffer. This is the default
framebuffer for sun4m machines and offers both 8-bit and 24-bit
colour depths at a fixed resolution of 1024x768.
cg3 (sun4m only) Sun cgthree framebuffer. This is a simple 8-bit
framebuffer for sun4m machines available in both 1024x768
(OpenBIOS) and 1152x900 (OBP) resolutions aimed at people
wishing to run older Solaris versions.
virtio
Virtio VGA card.
none
Disable VGA card.
-full-screen
Start in full screen.
-g widthxheight[xdepth]
Set the initial graphical resolution and depth (PPC, SPARC only).
-vnc display[,option[,option[,...]]]
Normally, if QEMU is compiled with graphical window support, it
displays output such as guest graphics, guest console, and the QEMU
monitor in a window. With this option, you can have QEMU listen on
VNC display display and redirect the VGA display over the VNC
session. It is very useful to enable the usb tablet device when
using this option (option -device usb-tablet). When using the VNC
display, you must use the -k parameter to set the keyboard layout
if you are not using en-us. Valid syntax for the display is
to=L
With this option, QEMU will try next available VNC displays,
until the number L, if the origianlly defined "-vnc display" is
not available, e.g. port 5900+display is already used by
another application. By default, to=0.
host:d
TCP connections will only be allowed from host on display d.
By convention the TCP port is 5900+d. Optionally, host can be
omitted in which case the server will accept connections from
any host.
unix:path
Connections will be allowed over UNIX domain sockets where path
is the location of a unix socket to listen for connections on.
none
VNC is initialized but not started. The monitor "change"
command can be used to later start the VNC server.
Following the display value there may be one or more option flags
separated by commas. Valid options are
reverse
Connect to a listening VNC client via a "reverse" connection.
The client is specified by the display. For reverse network
connections (host:d,"reverse"), the d argument is a TCP port
number, not a display number.
websocket
Opens an additional TCP listening port dedicated to VNC
Websocket connections. If a bare websocket option is given,
the Websocket port is 5700+display. An alternative port can be
specified with the syntax "websocket"=port.
If host is specified connections will only be allowed from this
host. It is possible to control the websocket listen address
independently, using the syntax "websocket"=host:port.
If no TLS credentials are provided, the websocket connection
runs in unencrypted mode. If TLS credentials are provided, the
websocket connection requires encrypted client connections.
password
Require that password based authentication is used for client
connections.
The password must be set separately using the "set_password"
command in the pcsys_monitor. The syntax to change your
password is: "set_password <protocol> <password>" where
<protocol> could be either "vnc" or "spice".
If you would like to change <protocol> password expiration, you
should use "expire_password <protocol> <expiration-time>" where
expiration time could be one of the following options: now,
never, +seconds or UNIX time of expiration, e.g. +60 to make
password expire in 60 seconds, or 1335196800 to make password
expire on "Mon Apr 23 12:00:00 EDT 2012" (UNIX time for this
date and time).
You can also use keywords "now" or "never" for the expiration
time to allow <protocol> password to expire immediately or
never expire.
tls-creds=ID
Provides the ID of a set of TLS credentials to use to secure
the VNC server. They will apply to both the normal VNC server
socket and the websocket socket (if enabled). Setting TLS
credentials will cause the VNC server socket to enable the
VeNCrypt auth mechanism. The credentials should have been
previously created using the -object tls-creds argument.
The tls-creds parameter obsoletes the tls, x509, and x509verify
options, and as such it is not permitted to set both new and
old type options at the same time.
tls Require that client use TLS when communicating with the VNC
server. This uses anonymous TLS credentials so is susceptible
to a man-in-the-middle attack. It is recommended that this
option be combined with either the x509 or x509verify options.
This option is now deprecated in favor of using the tls-creds
argument.
x509=/path/to/certificate/dir
Valid if tls is specified. Require that x509 credentials are
used for negotiating the TLS session. The server will send its
x509 certificate to the client. It is recommended that a
password be set on the VNC server to provide authentication of
the client when this is used. The path following this option
specifies where the x509 certificates are to be loaded from.
See the vnc_security section for details on generating
certificates.
This option is now deprecated in favour of using the tls-creds
argument.
x509verify=/path/to/certificate/dir
Valid if tls is specified. Require that x509 credentials are
used for negotiating the TLS session. The server will send its
x509 certificate to the client, and request that the client
send its own x509 certificate. The server will validate the
client's certificate against the CA certificate, and reject
clients when validation fails. If the certificate authority is
trusted, this is a sufficient authentication mechanism. You may
still wish to set a password on the VNC server as a second
authentication layer. The path following this option specifies
where the x509 certificates are to be loaded from. See the
vnc_security section for details on generating certificates.
This option is now deprecated in favour of using the tls-creds
argument.
sasl
Require that the client use SASL to authenticate with the VNC
server. The exact choice of authentication method used is
controlled from the system / user's SASL configuration file for
the 'qemu' service. This is typically found in
/etc/sasl2/qemu.conf. If running QEMU as an unprivileged user,
an environment variable SASL_CONF_PATH can be used to make it
search alternate locations for the service config. While some
SASL auth methods can also provide data encryption (eg GSSAPI),
it is recommended that SASL always be combined with the 'tls'
and 'x509' settings to enable use of SSL and server
certificates. This ensures a data encryption preventing
compromise of authentication credentials. See the vnc_security
section for details on using SASL authentication.
acl Turn on access control lists for checking of the x509 client
certificate and SASL party. For x509 certs, the ACL check is
made against the certificate's distinguished name. This is
something that looks like "C=GB,O=ACME,L=Boston,CN=bob". For
SASL party, the ACL check is made against the username, which
depending on the SASL plugin, may include a realm component, eg
"bob" or "bob@EXAMPLE.COM". When the acl flag is set, the
initial access list will be empty, with a "deny" policy. Thus
no one will be allowed to use the VNC server until the ACLs
have been loaded. This can be achieved using the "acl" monitor
command.
lossy
Enable lossy compression methods (gradient, JPEG, ...). If this
option is set, VNC client may receive lossy framebuffer updates
depending on its encoding settings. Enabling this option can
save a lot of bandwidth at the expense of quality.
non-adaptive
Disable adaptive encodings. Adaptive encodings are enabled by
default. An adaptive encoding will try to detect frequently
updated screen regions, and send updates in these regions using
a lossy encoding (like JPEG). This can be really helpful to
save bandwidth when playing videos. Disabling adaptive
encodings restores the original static behavior of encodings
like Tight.
share=[allow-exclusive|force-shared|ignore]
Set display sharing policy. 'allow-exclusive' allows clients
to ask for exclusive access. As suggested by the rfb spec this
is implemented by dropping other connections. Connecting
multiple clients in parallel requires all clients asking for a
shared session (vncviewer: -shared switch). This is the
default. 'force-shared' disables exclusive client access.
Useful for shared desktop sessions, where you don't want
someone forgetting specify -shared disconnect everybody else.
'ignore' completely ignores the shared flag and allows
everybody connect unconditionally. Doesn't conform to the rfb
spec but is traditional QEMU behavior.
key-delay-ms
Set keyboard delay, for key down and key up events, in
milliseconds. Default is 10. Keyboards are low-bandwidth
devices, so this slowdown can help the device and guest to keep
up and not lose events in case events are arriving in bulk.
Possible causes for the latter are flaky network connections,
or scripts for automated testing.
i386 target only
-win2k-hack
Use it when installing Windows 2000 to avoid a disk full bug. After
Windows 2000 is installed, you no longer need this option (this
option slows down the IDE transfers).
-no-fd-bootchk
Disable boot signature checking for floppy disks in BIOS. May be
needed to boot from old floppy disks.
-no-acpi
Disable ACPI (Advanced Configuration and Power Interface) support.
Use it if your guest OS complains about ACPI problems (PC target
machine only).
-no-hpet
Disable HPET support.
-acpitable
[sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n]
[,asl_compiler_id=str][,asl_compiler_rev=n][,data=file1[:file2]...]
Add ACPI table with specified header fields and context from
specified files. For file=, take whole ACPI table from the
specified files, including all ACPI headers (possible overridden by
other options). For data=, only data portion of the table is used,
all header information is specified in the command line. If a SLIC
table is supplied to QEMU, then the SLIC's oem_id and oem_table_id
fields will override the same in the RSDT and the FADT (a.k.a.
FACP), in order to ensure the field matches required by the
Microsoft SLIC spec and the ACPI spec.
-smbios file=binary
Load SMBIOS entry from binary file.
-smbios
type=0[,vendor=str][,version=str][,date=str][,release=%d.%d][,uefi=on|off]
Specify SMBIOS type 0 fields
-smbios
type=1[,manufacturer=str][,product=str][,version=str][,serial=str][,uuid=uuid][,sku=str][,family=str]
Specify SMBIOS type 1 fields
-smbios
type=2[,manufacturer=str][,product=str][,version=str][,serial=str][,asset=str][,location=str][,family=str]
Specify SMBIOS type 2 fields
-smbios
type=3[,manufacturer=str][,version=str][,serial=str][,asset=str][,sku=str]
Specify SMBIOS type 3 fields
-smbios
type=4[,sock_pfx=str][,manufacturer=str][,version=str][,serial=str][,asset=str][,part=str]
Specify SMBIOS type 4 fields
-smbios
type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str][,asset=str][,part=str][,speed=%d]
Specify SMBIOS type 17 fields
Network options
-nic
[tap|bridge|user|l2tpv3|vde|netmap|vhost-user|socket][,...][,mac=macaddr][,model=mn]
This option is a shortcut for configuring both the on-board
(default) guest NIC hardware and the host network backend in one
go. The host backend options are the same as with the corresponding
-netdev options below. The guest NIC model can be set with
model=modelname. Use model=help to list the available device
types. The hardware MAC address can be set with mac=macaddr.
The following two example do exactly the same, to show how -nic can
be used to shorten the command line length (note that the e1000 is
the default on i386, so the model=e1000 parameter could even be
omitted here, too):
qemu-system-i386 -netdev user,id=n1,ipv6=off -device e1000,netdev=n1,mac=52:54:98:76:54:32
qemu-system-i386 -nic user,ipv6=off,model=e1000,mac=52:54:98:76:54:32
-nic none
Indicate that no network devices should be configured. It is used
to override the default configuration (default NIC with "user" host
network backend) which is activated if no other networking options
are provided.
-netdev user,id=id[,option][,option][,...]
Configure user mode host network backend which requires no
administrator privilege to run. Valid options are:
id=id
Assign symbolic name for use in monitor commands.
ipv4=on|off and ipv6=on|off
Specify that either IPv4 or IPv6 must be enabled. If neither is
specified both protocols are enabled.
net=addr[/mask]
Set IP network address the guest will see. Optionally specify
the netmask, either in the form a.b.c.d or as number of valid
top-most bits. Default is 10.0.2.0/24.
host=addr
Specify the guest-visible address of the host. Default is the
2nd IP in the guest network, i.e. x.x.x.2.
ipv6-net=addr[/int]
Set IPv6 network address the guest will see (default is
fec0::/64). The network prefix is given in the usual
hexadecimal IPv6 address notation. The prefix size is optional,
and is given as the number of valid top-most bits (default is
64).
ipv6-host=addr
Specify the guest-visible IPv6 address of the host. Default is
the 2nd IPv6 in the guest network, i.e. xxxx::2.
restrict=on|off
If this option is enabled, the guest will be isolated, i.e. it
will not be able to contact the host and no guest IP packets
will be routed over the host to the outside. This option does
not affect any explicitly set forwarding rules.
hostname=name
Specifies the client hostname reported by the built-in DHCP
server.
dhcpstart=addr
Specify the first of the 16 IPs the built-in DHCP server can
assign. Default is the 15th to 31st IP in the guest network,
i.e. x.x.x.15 to x.x.x.31.
dns=addr
Specify the guest-visible address of the virtual nameserver.
The address must be different from the host address. Default is
the 3rd IP in the guest network, i.e. x.x.x.3.
ipv6-dns=addr
Specify the guest-visible address of the IPv6 virtual
nameserver. The address must be different from the host
address. Default is the 3rd IP in the guest network, i.e.
xxxx::3.
dnssearch=domain
Provides an entry for the domain-search list sent by the built-
in DHCP server. More than one domain suffix can be transmitted
by specifying this option multiple times. If supported, this
will cause the guest to automatically try to append the given
domain suffix(es) in case a domain name can not be resolved.
Example:
qemu-system-i386 -nic user,dnssearch=mgmt.example.org,dnssearch=example.org
tftp=dir
When using the user mode network stack, activate a built-in
TFTP server. The files in dir will be exposed as the root of a
TFTP server. The TFTP client on the guest must be configured
in binary mode (use the command "bin" of the Unix TFTP client).
bootfile=file
When using the user mode network stack, broadcast file as the
BOOTP filename. In conjunction with tftp, this can be used to
network boot a guest from a local directory.
Example (using pxelinux):
qemu-system-i386 -hda linux.img -boot n -device e1000,netdev=n1 \
-netdev user,id=n1,tftp=/path/to/tftp/files,bootfile=/pxelinux.0
smb=dir[,smbserver=addr]
When using the user mode network stack, activate a built-in SMB
server so that Windows OSes can access to the host files in dir
transparently. The IP address of the SMB server can be set to
addr. By default the 4th IP in the guest network is used, i.e.
x.x.x.4.
In the guest Windows OS, the line:
10.0.2.4 smbserver
must be added in the file C:\WINDOWS\LMHOSTS (for windows
9x/Me) or C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS (Windows
NT/2000).
Then dir can be accessed in \\smbserver\qemu.
Note that a SAMBA server must be installed on the host OS.
hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport
Redirect incoming TCP or UDP connections to the host port
hostport to the guest IP address guestaddr on guest port
guestport. If guestaddr is not specified, its value is x.x.x.15
(default first address given by the built-in DHCP server). By
specifying hostaddr, the rule can be bound to a specific host
interface. If no connection type is set, TCP is used. This
option can be given multiple times.
For example, to redirect host X11 connection from screen 1 to
guest screen 0, use the following:
# on the host
qemu-system-i386 -nic user,hostfwd=tcp:127.0.0.1:6001-:6000
# this host xterm should open in the guest X11 server
xterm -display :1
To redirect telnet connections from host port 5555 to telnet
port on the guest, use the following:
# on the host
qemu-system-i386 -nic user,hostfwd=tcp::5555-:23
telnet localhost 5555
Then when you use on the host "telnet localhost 5555", you
connect to the guest telnet server.
guestfwd=[tcp]:server:port-dev
guestfwd=[tcp]:server:port-cmd:command
Forward guest TCP connections to the IP address server on port
port to the character device dev or to a program executed by
cmd:command which gets spawned for each connection. This option
can be given multiple times.
You can either use a chardev directly and have that one used
throughout QEMU's lifetime, like in the following example:
# open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever
# the guest accesses it
qemu-system-i386 -nic user,guestfwd=tcp:10.0.2.100:1234-tcp:10.10.1.1:4321
Or you can execute a command on every TCP connection
established by the guest, so that QEMU behaves similar to an
inetd process for that virtual server:
# call "netcat 10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234
# and connect the TCP stream to its stdin/stdout
qemu-system-i386 -nic 'user,id=n1,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321'
Note: Legacy stand-alone options -tftp, -bootp, -smb and -redir are
still processed and applied to -net user. Mixing them with the new
configuration syntax gives undefined results. Their use for new
applications is discouraged as they will be removed from future
versions.
-netdev
tap,id=id[,fd=h][,ifname=name][,script=file][,downscript=dfile][,br=bridge][,helper=helper]
Configure a host TAP network backend with ID id.
Use the network script file to configure it and the network script
dfile to deconfigure it. If name is not provided, the OS
automatically provides one. The default network configure script is
/etc/qemu-ifup and the default network deconfigure script is
/etc/qemu-ifdown. Use script=no or downscript=no to disable script
execution.
If running QEMU as an unprivileged user, use the network helper
helper to configure the TAP interface and attach it to the bridge.
The default network helper executable is
/path/to/qemu-bridge-helper and the default bridge device is br0.
fd=h can be used to specify the handle of an already opened host
TAP interface.
Examples:
#launch a QEMU instance with the default network script
qemu-system-i386 linux.img -nic tap
#launch a QEMU instance with two NICs, each one connected
#to a TAP device
qemu-system-i386 linux.img \
-netdev tap,id=nd0,ifname=tap0 -device e1000,netdev=nd0 \
-netdev tap,id=nd1,ifname=tap1 -device rtl8139,netdev=nd1
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-i386 linux.img -device virtio-net-pci,netdev=n1 \
-netdev tap,id=n1,"helper=/path/to/qemu-bridge-helper"
-netdev bridge,id=id[,br=bridge][,helper=helper]
Connect a host TAP network interface to a host bridge device.
Use the network helper helper to configure the TAP interface and
attach it to the bridge. The default network helper executable is
/path/to/qemu-bridge-helper and the default bridge device is br0.
Examples:
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-i386 linux.img -netdev bridge,id=n1 -device virtio-net,netdev=n1
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge qemubr0
qemu-system-i386 linux.img -netdev bridge,br=qemubr0,id=n1 -device virtio-net,netdev=n1
-netdev socket,id=id[,fd=h][,listen=[host]:port][,connect=host:port]
This host network backend can be used to connect the guest's
network to another QEMU virtual machine using a TCP socket
connection. If listen is specified, QEMU waits for incoming
connections on port (host is optional). connect is used to connect
to another QEMU instance using the listen option. fd=h specifies an
already opened TCP socket.
Example:
# launch a first QEMU instance
qemu-system-i386 linux.img \
-device e1000,netdev=n1,mac=52:54:00:12:34:56 \
-netdev socket,id=n1,listen=:1234
# connect the network of this instance to the network of the first instance
qemu-system-i386 linux.img \
-device e1000,netdev=n2,mac=52:54:00:12:34:57 \
-netdev socket,id=n2,connect=127.0.0.1:1234
-netdev socket,id=id[,fd=h][,mcast=maddr:port[,localaddr=addr]]
Configure a socket host network backend to share the guest's
network traffic with another QEMU virtual machines using a UDP
multicast socket, effectively making a bus for every QEMU with same
multicast address maddr and port. NOTES:
1. Several QEMU can be running on different hosts and share same
bus (assuming correct multicast setup for these hosts).
2. mcast support is compatible with User Mode Linux (argument
ethN=mcast), see <http://user-mode-linux.sf.net>.
3. Use fd=h to specify an already opened UDP multicast socket.
Example:
# launch one QEMU instance
qemu-system-i386 linux.img \
-device e1000,netdev=n1,mac=52:54:00:12:34:56 \
-netdev socket,id=n1,mcast=230.0.0.1:1234
# launch another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-device e1000,netdev=n2,mac=52:54:00:12:34:57 \
-netdev socket,id=n2,mcast=230.0.0.1:1234
# launch yet another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-device e1000,netdev=n3,macaddr=52:54:00:12:34:58 \
-netdev socket,id=n3,mcast=230.0.0.1:1234
Example (User Mode Linux compat.):
# launch QEMU instance (note mcast address selected is UML's default)
qemu-system-i386 linux.img \
-device e1000,netdev=n1,mac=52:54:00:12:34:56 \
-netdev socket,id=n1,mcast=239.192.168.1:1102
# launch UML
/path/to/linux ubd0=/path/to/root_fs eth0=mcast
Example (send packets from host's 1.2.3.4):
qemu-system-i386 linux.img \
-device e1000,netdev=n1,mac=52:54:00:12:34:56 \
-netdev socket,id=n1,mcast=239.192.168.1:1102,localaddr=1.2.3.4
-netdev
l2tpv3,id=id,src=srcaddr,dst=dstaddr[,srcport=srcport][,dstport=dstport],txsession=txsession[,rxsession=rxsession][,ipv6][,udp][,cookie64][,counter][,pincounter][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset]
Configure a L2TPv3 pseudowire host network backend. L2TPv3
(RFC3391) is a popular protocol to transport Ethernet (and other
Layer 2) data frames between two systems. It is present in routers,
firewalls and the Linux kernel (from version 3.3 onwards).
This transport allows a VM to communicate to another VM, router or
firewall directly.
src=srcaddr
source address (mandatory)
dst=dstaddr
destination address (mandatory)
udp select udp encapsulation (default is ip).
srcport=srcport
source udp port.
dstport=dstport
destination udp port.
ipv6
force v6, otherwise defaults to v4.
rxcookie=rxcookie
txcookie=txcookie
Cookies are a weak form of security in the l2tpv3
specification. Their function is mostly to prevent
misconfiguration. By default they are 32 bit.
cookie64
Set cookie size to 64 bit instead of the default 32
counter=off
Force a 'cut-down' L2TPv3 with no counter as in
draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00
pincounter=on
Work around broken counter handling in peer. This may also help
on networks which have packet reorder.
offset=offset
Add an extra offset between header and data
For example, to attach a VM running on host 4.3.2.1 via L2TPv3 to
the bridge br-lan on the remote Linux host 1.2.3.4:
# Setup tunnel on linux host using raw ip as encapsulation
# on 1.2.3.4
ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \
encap udp udp_sport 16384 udp_dport 16384
ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \
0xFFFFFFFF peer_session_id 0xFFFFFFFF
ifconfig vmtunnel0 mtu 1500
ifconfig vmtunnel0 up
brctl addif br-lan vmtunnel0
# on 4.3.2.1
# launch QEMU instance - if your network has reorder or is very lossy add ,pincounter
qemu-system-i386 linux.img -device e1000,netdev=n1 \
-netdev l2tpv3,id=n1,src=4.2.3.1,dst=1.2.3.4,udp,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter
-netdev
vde,id=id[,sock=socketpath][,port=n][,group=groupname][,mode=octalmode]
Configure VDE backend to connect to PORT n of a vde switch running
on host and listening for incoming connections on socketpath. Use
GROUP groupname and MODE octalmode to change default ownership and
permissions for communication port. This option is only available
if QEMU has been compiled with vde support enabled.
Example:
# launch vde switch
vde_switch -F -sock /tmp/myswitch
# launch QEMU instance
qemu-system-i386 linux.img -nic vde,sock=/tmp/myswitch
-netdev vhost-user,chardev=id[,vhostforce=on|off][,queues=n]
Establish a vhost-user netdev, backed by a chardev id. The chardev
should be a unix domain socket backed one. The vhost-user uses a
specifically defined protocol to pass vhost ioctl replacement
messages to an application on the other end of the socket. On non-
MSIX guests, the feature can be forced with vhostforce. Use
'queues=n' to specify the number of queues to be created for
multiqueue vhost-user.
Example:
qemu -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \
-numa node,memdev=mem \
-chardev socket,id=chr0,path=/path/to/socket \
-netdev type=vhost-user,id=net0,chardev=chr0 \
-device virtio-net-pci,netdev=net0
-netdev hubport,id=id,hubid=hubid[,netdev=nd]
Create a hub port on the emulated hub with ID hubid.
The hubport netdev lets you connect a NIC to a QEMU emulated hub
instead of a single netdev. "-net" and "-device" with the parameter
vlan (deprecated), or "-nic hubport" can also be used to connect a
network device or a NIC to a hub. Alternatively, you can also
connect the hubport to another netdev with ID nd by using the
netdev=nd option.
-net nic[,vlan=n][,netdev=nd][,macaddr=mac][,model=type]
[,name=name][,addr=addr][,vectors=v]
Legacy option to configure or create an on-board (or machine
default) Network Interface Card(NIC) and connect it either to the
emulated hub port ("vlan") with number n (n = 0 is the default), or
to the netdev nd. The NIC is an e1000 by default on the PC target.
Optionally, the MAC address can be changed to mac, the device
address set to addr (PCI cards only), and a name can be assigned
for use in monitor commands. Optionally, for PCI cards, you can
specify the number v of MSI-X vectors that the card should have;
this option currently only affects virtio cards; set v = 0 to
disable MSI-X. If no -net option is specified, a single NIC is
created. QEMU can emulate several different models of network
card. Use "-net nic,model=help" for a list of available devices
for your target.
-net user|tap|bridge|socket|l2tpv3|vde[,...][,vlan=n][,name=name]
Configure a host network backend (with the options corresponding to
the same -netdev option) and connect it to the emulated hub
("vlan") with the number n (default is number 0). Use name to
specify the name of the hub port.
Character device options
The general form of a character device option is:
-chardev backend,id=id[,mux=on|off][,options]
Backend is one of: null, socket, udp, msmouse, vc, ringbuf, file,
pipe, console, serial, pty, stdio, braille, tty, parallel, parport,
spicevmc, spiceport. The specific backend will determine the
applicable options.
Use "-chardev help" to print all available chardev backend types.
All devices must have an id, which can be any string up to 127
characters long. It is used to uniquely identify this device in
other command line directives.
A character device may be used in multiplexing mode by multiple
front-ends. Specify mux=on to enable this mode. A multiplexer is
a "1:N" device, and here the "1" end is your specified chardev
backend, and the "N" end is the various parts of QEMU that can talk
to a chardev. If you create a chardev with id=myid and mux=on,
QEMU will create a multiplexer with your specified ID, and you can
then configure multiple front ends to use that chardev ID for their
input/output. Up to four different front ends can be connected to a
single multiplexed chardev. (Without multiplexing enabled, a
chardev can only be used by a single front end.) For instance you
could use this to allow a single stdio chardev to be used by two
serial ports and the QEMU monitor:
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-serial chardev:char0 \
-serial chardev:char0
You can have more than one multiplexer in a system configuration;
for instance you could have a TCP port multiplexed between UART 0
and UART 1, and stdio multiplexed between the QEMU monitor and a
parallel port:
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-parallel chardev:char0 \
-chardev tcp,...,mux=on,id=char1 \
-serial chardev:char1 \
-serial chardev:char1
When you're using a multiplexed character device, some escape
sequences are interpreted in the input.
Note that some other command line options may implicitly create
multiplexed character backends; for instance -serial mon:stdio
creates a multiplexed stdio backend connected to the serial port
and the QEMU monitor, and -nographic also multiplexes the console
and the monitor to stdio.
There is currently no support for multiplexing in the other
direction (where a single QEMU front end takes input and output
from multiple chardevs).
Every backend supports the logfile option, which supplies the path
to a file to record all data transmitted via the backend. The
logappend option controls whether the log file will be truncated or
appended to when opened.
The available backends are:
-chardev null,id=id
A void device. This device will not emit any data, and will drop
any data it receives. The null backend does not take any options.
-chardev socket,id=id[,TCP options or unix
options][,server][,nowait][,telnet][,reconnect=seconds][,tls-creds=id]
Create a two-way stream socket, which can be either a TCP or a unix
socket. A unix socket will be created if path is specified.
Behaviour is undefined if TCP options are specified for a unix
socket.
server specifies that the socket shall be a listening socket.
nowait specifies that QEMU should not block waiting for a client to
connect to a listening socket.
telnet specifies that traffic on the socket should interpret telnet
escape sequences.
reconnect sets the timeout for reconnecting on non-server sockets
when the remote end goes away. qemu will delay this many seconds
and then attempt to reconnect. Zero disables reconnecting, and is
the default.
tls-creds requests enablement of the TLS protocol for encryption,
and specifies the id of the TLS credentials to use for the
handshake. The credentials must be previously created with the
-object tls-creds argument.
TCP and unix socket options are given below:
TCP options: port=port[,host=host][,to=to][,ipv4][,ipv6][,nodelay]
host for a listening socket specifies the local address to be
bound. For a connecting socket species the remote host to
connect to. host is optional for listening sockets. If not
specified it defaults to 0.0.0.0.
port for a listening socket specifies the local port to be
bound. For a connecting socket specifies the port on the remote
host to connect to. port can be given as either a port number
or a service name. port is required.
to is only relevant to listening sockets. If it is specified,
and port cannot be bound, QEMU will attempt to bind to
subsequent ports up to and including to until it succeeds. to
must be specified as a port number.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be used.
If neither is specified the socket may use either protocol.
nodelay disables the Nagle algorithm.
unix options: path=path
path specifies the local path of the unix socket. path is
required.
-chardev
udp,id=id[,host=host],port=port[,localaddr=localaddr][,localport=localport][,ipv4][,ipv6]
Sends all traffic from the guest to a remote host over UDP.
host specifies the remote host to connect to. If not specified it
defaults to "localhost".
port specifies the port on the remote host to connect to. port is
required.
localaddr specifies the local address to bind to. If not specified
it defaults to 0.0.0.0.
localport specifies the local port to bind to. If not specified any
available local port will be used.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be used. If
neither is specified the device may use either protocol.
-chardev msmouse,id=id
Forward QEMU's emulated msmouse events to the guest. msmouse does
not take any options.
-chardev
vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]
Connect to a QEMU text console. vc may optionally be given a
specific size.
width and height specify the width and height respectively of the
console, in pixels.
cols and rows specify that the console be sized to fit a text
console with the given dimensions.
-chardev ringbuf,id=id[,size=size]
Create a ring buffer with fixed size size. size must be a power of
two and defaults to "64K".
-chardev file,id=id,path=path
Log all traffic received from the guest to a file.
path specifies the path of the file to be opened. This file will be
created if it does not already exist, and overwritten if it does.
path is required.
-chardev pipe,id=id,path=path
Create a two-way connection to the guest. The behaviour differs
slightly between Windows hosts and other hosts:
On Windows, a single duplex pipe will be created at \\.pipe\path.
On other hosts, 2 pipes will be created called path.in and
path.out. Data written to path.in will be received by the guest.
Data written by the guest can be read from path.out. QEMU will not
create these fifos, and requires them to be present.
path forms part of the pipe path as described above. path is
required.
-chardev console,id=id
Send traffic from the guest to QEMU's standard output. console does
not take any options.
console is only available on Windows hosts.
-chardev serial,id=id,path=path
Send traffic from the guest to a serial device on the host.
On Unix hosts serial will actually accept any tty device, not only
serial lines.
path specifies the name of the serial device to open.
-chardev pty,id=id
Create a new pseudo-terminal on the host and connect to it. pty
does not take any options.
pty is not available on Windows hosts.
-chardev stdio,id=id[,signal=on|off]
Connect to standard input and standard output of the QEMU process.
signal controls if signals are enabled on the terminal, that
includes exiting QEMU with the key sequence Control-c. This option
is enabled by default, use signal=off to disable it.
-chardev braille,id=id
Connect to a local BrlAPI server. braille does not take any
options.
-chardev tty,id=id,path=path
tty is only available on Linux, Sun, FreeBSD, NetBSD, OpenBSD and
DragonFlyBSD hosts. It is an alias for serial.
path specifies the path to the tty. path is required.
-chardev parallel,id=id,path=path
-chardev parport,id=id,path=path
parallel is only available on Linux, FreeBSD and DragonFlyBSD
hosts.
Connect to a local parallel port.
path specifies the path to the parallel port device. path is
required.
-chardev spicevmc,id=id,debug=debug,name=name
spicevmc is only available when spice support is built in.
debug debug level for spicevmc
name name of spice channel to connect to
Connect to a spice virtual machine channel, such as vdiport.
-chardev spiceport,id=id,debug=debug,name=name
spiceport is only available when spice support is built in.
debug debug level for spicevmc
name name of spice port to connect to
Connect to a spice port, allowing a Spice client to handle the
traffic identified by a name (preferably a fqdn).
Bluetooth(R) options
-bt hci[...]
Defines the function of the corresponding Bluetooth HCI. -bt
options are matched with the HCIs present in the chosen machine
type. For example when emulating a machine with only one HCI built
into it, only the first "-bt hci[...]" option is valid and defines
the HCI's logic. The Transport Layer is decided by the machine
type. Currently the machines "n800" and "n810" have one HCI and
all other machines have none.
The following three types are recognized:
-bt hci,null
(default) The corresponding Bluetooth HCI assumes no internal
logic and will not respond to any HCI commands or emit events.
-bt hci,host[:id]
("bluez" only) The corresponding HCI passes commands / events
to / from the physical HCI identified by the name id (default:
"hci0") on the computer running QEMU. Only available on
"bluez" capable systems like Linux.
-bt hci[,vlan=n]
Add a virtual, standard HCI that will participate in the
Bluetooth scatternet n (default 0). Similarly to -net VLANs,
devices inside a bluetooth network n can only communicate with
other devices in the same network (scatternet).
-bt vhci[,vlan=n]
(Linux-host only) Create a HCI in scatternet n (default 0) attached
to the host bluetooth stack instead of to the emulated target.
This allows the host and target machines to participate in a common
scatternet and communicate. Requires the Linux "vhci" driver
installed. Can be used as following:
qemu-system-i386 [...OPTIONS...] -bt hci,vlan=5 -bt vhci,vlan=5
-bt device:dev[,vlan=n]
Emulate a bluetooth device dev and place it in network n (default
0). QEMU can only emulate one type of bluetooth devices currently:
keyboard
Virtual wireless keyboard implementing the HIDP bluetooth
profile.
TPM device options
The general form of a TPM device option is:
-tpmdev backend,id=id[,options]
The specific backend type will determine the applicable options.
The "-tpmdev" option creates the TPM backend and requires a
"-device" option that specifies the TPM frontend interface model.
Use "-tpmdev help" to print all available TPM backend types.
The available backends are:
-tpmdev passthrough,id=id,path=path,cancel-path=cancel-path
(Linux-host only) Enable access to the host's TPM using the
passthrough driver.
path specifies the path to the host's TPM device, i.e., on a Linux
host this would be "/dev/tpm0". path is optional and by default
"/dev/tpm0" is used.
cancel-path specifies the path to the host TPM device's sysfs entry
allowing for cancellation of an ongoing TPM command. cancel-path
is optional and by default QEMU will search for the sysfs entry to
use.
Some notes about using the host's TPM with the passthrough driver:
The TPM device accessed by the passthrough driver must not be used
by any other application on the host.
Since the host's firmware (BIOS/UEFI) has already initialized the
TPM, the VM's firmware (BIOS/UEFI) will not be able to initialize
the TPM again and may therefore not show a TPM-specific menu that
would otherwise allow the user to configure the TPM, e.g., allow
the user to enable/disable or activate/deactivate the TPM.
Further, if TPM ownership is released from within a VM then the
host's TPM will get disabled and deactivated. To enable and
activate the TPM again afterwards, the host has to be rebooted and
the user is required to enter the firmware's menu to enable and
activate the TPM. If the TPM is left disabled and/or deactivated
most TPM commands will fail.
To create a passthrough TPM use the following two options:
-tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0
Note that the "-tpmdev" id is "tpm0" and is referenced by
"tpmdev=tpm0" in the device option.
-tpmdev emulator,id=id,chardev=dev
(Linux-host only) Enable access to a TPM emulator using Unix domain
socket based chardev backend.
chardev specifies the unique ID of a character device backend that
provides connection to the software TPM server.
To create a TPM emulator backend device with chardev socket
backend:
-chardev socket,id=chrtpm,path=/tmp/swtpm-sock -tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0
Linux/Multiboot boot specific
When using these options, you can use a given Linux or Multiboot kernel
without installing it in the disk image. It can be useful for easier
testing of various kernels.
-kernel bzImage
Use bzImage as kernel image. The kernel can be either a Linux
kernel or in multiboot format.
-append cmdline
Use cmdline as kernel command line
-initrd file
Use file as initial ram disk.
-initrd "file1 arg=foo,file2"
This syntax is only available with multiboot.
Use file1 and file2 as modules and pass arg=foo as parameter to the
first module.
-dtb file
Use file as a device tree binary (dtb) image and pass it to the
kernel on boot.
Debug/Expert options
-fw_cfg [name=]name,file=file
Add named fw_cfg entry with contents from file file.
-fw_cfg [name=]name,string=str
Add named fw_cfg entry with contents from string str.
The terminating NUL character of the contents of str will not be
included as part of the fw_cfg item data. To insert contents with
embedded NUL characters, you have to use the file parameter.
The fw_cfg entries are passed by QEMU through to the guest.
Example:
-fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin
creates an fw_cfg entry named opt/com.mycompany/blob with contents
from ./my_blob.bin.
-serial dev
Redirect the virtual serial port to host character device dev. The
default device is "vc" in graphical mode and "stdio" in non
graphical mode.
This option can be used several times to simulate up to 4 serial
ports.
Use "-serial none" to disable all serial ports.
Available character devices are:
vc[:WxH]
Virtual console. Optionally, a width and height can be given in
pixel with
vc:800x600
It is also possible to specify width or height in characters:
vc:80Cx24C
pty [Linux only] Pseudo TTY (a new PTY is automatically allocated)
none
No device is allocated.
null
void device
chardev:id
Use a named character device defined with the "-chardev"
option.
/dev/XXX
[Linux only] Use host tty, e.g. /dev/ttyS0. The host serial
port parameters are set according to the emulated ones.
/dev/parportN
[Linux only, parallel port only] Use host parallel port N.
Currently SPP and EPP parallel port features can be used.
file:filename
Write output to filename. No character can be read.
stdio
[Unix only] standard input/output
pipe:filename
name pipe filename
COMn
[Windows only] Use host serial port n
udp:[remote_host]:remote_port[@[src_ip]:src_port]
This implements UDP Net Console. When remote_host or src_ip
are not specified they default to 0.0.0.0. When not using a
specified src_port a random port is automatically chosen.
If you just want a simple readonly console you can use "netcat"
or "nc", by starting QEMU with: "-serial udp::4555" and nc as:
"nc -u -l -p 4555". Any time QEMU writes something to that port
it will appear in the netconsole session.
If you plan to send characters back via netconsole or you want
to stop and start QEMU a lot of times, you should have QEMU use
the same source port each time by using something like "-serial
udp::4555@4556" to QEMU. Another approach is to use a patched
version of netcat which can listen to a TCP port and send and
receive characters via udp. If you have a patched version of
netcat which activates telnet remote echo and single char
transfer, then you can use the following options to set up a
netcat redirector to allow telnet on port 5555 to access the
QEMU port.
"QEMU Options:"
-serial udp::4555@4556
"netcat options:"
-u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T
"telnet options:"
localhost 5555
tcp:[host]:port[,server][,nowait][,nodelay][,reconnect=seconds]
The TCP Net Console has two modes of operation. It can send
the serial I/O to a location or wait for a connection from a
location. By default the TCP Net Console is sent to host at
the port. If you use the server option QEMU will wait for a
client socket application to connect to the port before
continuing, unless the "nowait" option was specified. The
"nodelay" option disables the Nagle buffering algorithm. The
"reconnect" option only applies if noserver is set, if the
connection goes down it will attempt to reconnect at the given
interval. If host is omitted, 0.0.0.0 is assumed. Only one TCP
connection at a time is accepted. You can use "telnet" to
connect to the corresponding character device.
"Example to send tcp console to 192.168.0.2 port 4444"
-serial tcp:192.168.0.2:4444
"Example to listen and wait on port 4444 for connection"
-serial tcp::4444,server
"Example to not wait and listen on ip 192.168.0.100 port 4444"
-serial tcp:192.168.0.100:4444,server,nowait
telnet:host:port[,server][,nowait][,nodelay]
The telnet protocol is used instead of raw tcp sockets. The
options work the same as if you had specified "-serial tcp".
The difference is that the port acts like a telnet server or
client using telnet option negotiation. This will also allow
you to send the MAGIC_SYSRQ sequence if you use a telnet that
supports sending the break sequence. Typically in unix telnet
you do it with Control-] and then type "send break" followed by
pressing the enter key.
unix:path[,server][,nowait][,reconnect=seconds]
A unix domain socket is used instead of a tcp socket. The
option works the same as if you had specified "-serial tcp"
except the unix domain socket path is used for connections.
mon:dev_string
This is a special option to allow the monitor to be multiplexed
onto another serial port. The monitor is accessed with key
sequence of Control-a and then pressing c. dev_string should
be any one of the serial devices specified above. An example
to multiplex the monitor onto a telnet server listening on port
4444 would be:
"-serial mon:telnet::4444,server,nowait"
When the monitor is multiplexed to stdio in this way, Ctrl+C
will not terminate QEMU any more but will be passed to the
guest instead.
braille
Braille device. This will use BrlAPI to display the braille
output on a real or fake device.
msmouse
Three button serial mouse. Configure the guest to use Microsoft
protocol.
-parallel dev
Redirect the virtual parallel port to host device dev (same devices
as the serial port). On Linux hosts, /dev/parportN can be used to
use hardware devices connected on the corresponding host parallel
port.
This option can be used several times to simulate up to 3 parallel
ports.
Use "-parallel none" to disable all parallel ports.
-monitor dev
Redirect the monitor to host device dev (same devices as the serial
port). The default device is "vc" in graphical mode and "stdio" in
non graphical mode. Use "-monitor none" to disable the default
monitor.
-qmp dev
Like -monitor but opens in 'control' mode.
-qmp-pretty dev
Like -qmp but uses pretty JSON formatting.
-mon [chardev=]name[,mode=readline|control][,pretty[=on|off]]
Setup monitor on chardev name. "pretty" turns on JSON pretty
printing easing human reading and debugging.
-debugcon dev
Redirect the debug console to host device dev (same devices as the
serial port). The debug console is an I/O port which is typically
port 0xe9; writing to that I/O port sends output to this device.
The default device is "vc" in graphical mode and "stdio" in non
graphical mode.
-pidfile file
Store the QEMU process PID in file. It is useful if you launch QEMU
from a script.
-singlestep
Run the emulation in single step mode.
-S Do not start CPU at startup (you must type 'c' in the monitor).
-realtime mlock=on|off
Run qemu with realtime features. mlocking qemu and guest memory
can be enabled via mlock=on (enabled by default).
-gdb dev
Wait for gdb connection on device dev. Typical connections will
likely be TCP-based, but also UDP, pseudo TTY, or even stdio are
reasonable use case. The latter is allowing to start QEMU from
within gdb and establish the connection via a pipe:
(gdb) target remote | exec qemu-system-i386 -gdb stdio ...
-s Shorthand for -gdb tcp::1234, i.e. open a gdbserver on TCP port
1234.
-d item1[,...]
Enable logging of specified items. Use '-d help' for a list of log
items.
-D logfile
Output log in logfile instead of to stderr
-dfilter range1[,...]
Filter debug output to that relevant to a range of target
addresses. The filter spec can be either start+size, start-size or
start..end where start end and size are the addresses and sizes
required. For example:
-dfilter 0x8000..0x8fff,0xffffffc000080000+0x200,0xffffffc000060000-0x1000
Will dump output for any code in the 0x1000 sized block starting at
0x8000 and the 0x200 sized block starting at 0xffffffc000080000 and
another 0x1000 sized block starting at 0xffffffc00005f000.
-L path
Set the directory for the BIOS, VGA BIOS and keymaps.
To list all the data directories, use "-L help".
-bios file
Set the filename for the BIOS.
-enable-kvm
Enable KVM full virtualization support. This option is only
available if KVM support is enabled when compiling.
-enable-hax
Enable HAX (Hardware-based Acceleration eXecution) support. This
option is only available if HAX support is enabled when compiling.
HAX is only applicable to MAC and Windows platform, and thus does
not conflict with KVM.
-xen-domid id
Specify xen guest domain id (XEN only).
-xen-create
Create domain using xen hypercalls, bypassing xend. Warning:
should not be used when xend is in use (XEN only).
-xen-attach
Attach to existing xen domain. xend will use this when starting
QEMU (XEN only). Restrict set of available xen operations to
specified domain id (XEN only).
-no-reboot
Exit instead of rebooting.
-no-shutdown
Don't exit QEMU on guest shutdown, but instead only stop the
emulation. This allows for instance switching to monitor to commit
changes to the disk image.
-loadvm file
Start right away with a saved state ("loadvm" in monitor)
-daemonize
Daemonize the QEMU process after initialization. QEMU will not
detach from standard IO until it is ready to receive connections on
any of its devices. This option is a useful way for external
programs to launch QEMU without having to cope with initialization
race conditions.
-option-rom file
Load the contents of file as an option ROM. This option is useful
to load things like EtherBoot.
-rtc [base=utc|localtime|date][,clock=host|vm][,driftfix=none|slew]
Specify base as "utc" or "localtime" to let the RTC start at the
current UTC or local time, respectively. "localtime" is required
for correct date in MS-DOS or Windows. To start at a specific point
in time, provide date in the format "2006-06-17T16:01:21" or
"2006-06-17". The default base is UTC.
By default the RTC is driven by the host system time. This allows
using of the RTC as accurate reference clock inside the guest,
specifically if the host time is smoothly following an accurate
external reference clock, e.g. via NTP. If you want to isolate the
guest time from the host, you can set clock to "rt" instead. To
even prevent it from progressing during suspension, you can set it
to "vm".
Enable driftfix (i386 targets only) if you experience time drift
problems, specifically with Windows' ACPI HAL. This option will try
to figure out how many timer interrupts were not processed by the
Windows guest and will re-inject them.
-icount
[shift=N|auto][,rr=record|replay,rrfile=filename,rrsnapshot=snapshot]
Enable virtual instruction counter. The virtual cpu will execute
one instruction every 2^N ns of virtual time. If "auto" is
specified then the virtual cpu speed will be automatically adjusted
to keep virtual time within a few seconds of real time.
When the virtual cpu is sleeping, the virtual time will advance at
default speed unless sleep=on|off is specified. With sleep=on|off,
the virtual time will jump to the next timer deadline instantly
whenever the virtual cpu goes to sleep mode and will not advance if
no timer is enabled. This behavior give deterministic execution
times from the guest point of view.
Note that while this option can give deterministic behavior, it
does not provide cycle accurate emulation. Modern CPUs contain
superscalar out of order cores with complex cache hierarchies. The
number of instructions executed often has little or no correlation
with actual performance.
align=on will activate the delay algorithm which will try to
synchronise the host clock and the virtual clock. The goal is to
have a guest running at the real frequency imposed by the shift
option. Whenever the guest clock is behind the host clock and if
align=on is specified then we print a message to the user to inform
about the delay. Currently this option does not work when shift is
"auto". Note: The sync algorithm will work for those shift values
for which the guest clock runs ahead of the host clock. Typically
this happens when the shift value is high (how high depends on the
host machine).
When rr option is specified deterministic record/replay is enabled.
Replay log is written into filename file in record mode and read
from this file in replay mode.
Option rrsnapshot is used to create new vm snapshot named snapshot
at the start of execution recording. In replay mode this option is
used to load the initial VM state.
-watchdog model
Create a virtual hardware watchdog device. Once enabled (by a
guest action), the watchdog must be periodically polled by an agent
inside the guest or else the guest will be restarted. Choose a
model for which your guest has drivers.
The model is the model of hardware watchdog to emulate. Use
"-watchdog help" to list available hardware models. Only one
watchdog can be enabled for a guest.
The following models may be available:
ib700
iBASE 700 is a very simple ISA watchdog with a single timer.
i6300esb
Intel 6300ESB I/O controller hub is a much more featureful PCI-
based dual-timer watchdog.
diag288
A virtual watchdog for s390x backed by the diagnose 288
hypercall (currently KVM only).
-watchdog-action action
The action controls what QEMU will do when the watchdog timer
expires. The default is "reset" (forcefully reset the guest).
Other possible actions are: "shutdown" (attempt to gracefully
shutdown the guest), "poweroff" (forcefully poweroff the guest),
"inject-nmi" (inject a NMI into the guest), "pause" (pause the
guest), "debug" (print a debug message and continue), or "none" (do
nothing).
Note that the "shutdown" action requires that the guest responds to
ACPI signals, which it may not be able to do in the sort of
situations where the watchdog would have expired, and thus
"-watchdog-action shutdown" is not recommended for production use.
Examples:
"-watchdog i6300esb -watchdog-action pause"
"-watchdog ib700"
-echr numeric_ascii_value
Change the escape character used for switching to the monitor when
using monitor and serial sharing. The default is 0x01 when using
the "-nographic" option. 0x01 is equal to pressing "Control-a".
You can select a different character from the ascii control keys
where 1 through 26 map to Control-a through Control-z. For
instance you could use the either of the following to change the
escape character to Control-t.
"-echr 0x14"
"-echr 20"
-virtioconsole c
Set virtio console.
This option is maintained for backward compatibility.
Please use "-device virtconsole" for the new way of invocation.
-show-cursor
Show cursor.
-tb-size n
Set TB size.
-incoming tcp:[host]:port[,to=maxport][,ipv4][,ipv6]
-incoming rdma:host:port[,ipv4][,ipv6]
Prepare for incoming migration, listen on a given tcp port.
-incoming unix:socketpath
Prepare for incoming migration, listen on a given unix socket.
-incoming fd:fd
Accept incoming migration from a given filedescriptor.
-incoming exec:cmdline
Accept incoming migration as an output from specified external
command.
-incoming defer
Wait for the URI to be specified via migrate_incoming. The monitor
can be used to change settings (such as migration parameters) prior
to issuing the migrate_incoming to allow the migration to begin.
-only-migratable
Only allow migratable devices. Devices will not be allowed to enter
an unmigratable state.
-nodefaults
Don't create default devices. Normally, QEMU sets the default
devices like serial port, parallel port, virtual console, monitor
device, VGA adapter, floppy and CD-ROM drive and others. The
"-nodefaults" option will disable all those default devices.
-chroot dir
Immediately before starting guest execution, chroot to the
specified directory. Especially useful in combination with -runas.
-runas user
Immediately before starting guest execution, drop root privileges,
switching to the specified user.
-prom-env variable=value
Set OpenBIOS nvram variable to given value (PPC, SPARC only).
-semihosting
Enable semihosting mode (ARM, M68K, Xtensa, MIPS only).
-semihosting-config
[enable=on|off][,target=native|gdb|auto][,arg=str[,...]]
Enable and configure semihosting (ARM, M68K, Xtensa, MIPS only).
target="native|gdb|auto"
Defines where the semihosting calls will be addressed, to QEMU
("native") or to GDB ("gdb"). The default is "auto", which
means "gdb" during debug sessions and "native" otherwise.
arg=str1,arg=str2,...
Allows the user to pass input arguments, and can be used
multiple times to build up a list. The old-style
"-kernel"/"-append" method of passing a command line is still
supported for backward compatibility. If both the
"--semihosting-config arg" and the "-kernel"/"-append" are
specified, the former is passed to semihosting as it always
takes precedence.
-old-param
Old param mode (ARM only).
-sandbox
arg[,obsolete=string][,elevateprivileges=string][,spawn=string][,resourcecontrol=string]
Enable Seccomp mode 2 system call filter. 'on' will enable syscall
filtering and 'off' will disable it. The default is 'off'.
obsolete=string
Enable Obsolete system calls
elevateprivileges=string
Disable set*uid|gid system calls
spawn=string
Disable *fork and execve
resourcecontrol=string
Disable process affinity and schedular priority
-readconfig file
Read device configuration from file. This approach is useful when
you want to spawn QEMU process with many command line options but
you don't want to exceed the command line character limit.
-writeconfig file
Write device configuration to file. The file can be either filename
to save command line and device configuration into file or dash
"-") character to print the output to stdout. This can be later
used as input file for "-readconfig" option.
-no-user-config
The "-no-user-config" option makes QEMU not load any of the user-
provided config files on sysconfdir.
-trace [[enable=]pattern][,events=file][,file=file]
Specify tracing options.
[enable=]pattern
Immediately enable events matching pattern. The file must
contain one event name (as listed in the trace-events-all file)
per line; globbing patterns are accepted too. This option is
only available if QEMU has been compiled with the simple, log
or ftrace tracing backend. To specify multiple events or
patterns, specify the -trace option multiple times.
Use "-trace help" to print a list of names of trace points.
events=file
Immediately enable events listed in file. The file must
contain one event name (as listed in the trace-events-all file)
per line; globbing patterns are accepted too. This option is
only available if QEMU has been compiled with the simple, log
or ftrace tracing backend.
file=file
Log output traces to file. This option is only available if
QEMU has been compiled with the simple tracing backend.
-enable-fips
Enable FIPS 140-2 compliance mode.
-msg timestamp[=on|off]
prepend a timestamp to each log message.(default:on)
-dump-vmstate file
Dump json-encoded vmstate information for current machine type to
file in file
Generic object creation
-object typename[,prop1=value1,...]
Create a new object of type typename setting properties in the
order they are specified. Note that the 'id' property must be set.
These objects are placed in the '/objects' path.
-object
memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-
nodes,policy=default|preferred|bind|interleave,align=align
Creates a memory file backend object, which can be used to back
the guest RAM with huge pages.
The id parameter is a unique ID that will be used to reference
this memory region when configuring the -numa argument.
The size option provides the size of the memory region, and
accepts common suffixes, eg 500M.
The mem-path provides the path to either a shared memory or
huge page filesystem mount.
The share boolean option determines whether the memory region
is marked as private to QEMU, or shared. The latter allows a
co-operating external process to access the QEMU memory region.
The share is also required for pvrdma devices due to
limitations in the RDMA API provided by Linux.
Setting share=on might affect the ability to configure NUMA
bindings for the memory backend under some circumstances, see
Documentation/vm/numa_memory_policy.txt on the Linux kernel
source tree for additional details.
Setting the discard-data boolean option to on indicates that
file contents can be destroyed when QEMU exits, to avoid
unnecessarily flushing data to the backing file. Note that
discard-data is only an optimization, and QEMU might not
discard file contents if it aborts unexpectedly or is
terminated using SIGKILL.
The merge boolean option enables memory merge, also known as
MADV_MERGEABLE, so that Kernel Samepage Merging will consider
the pages for memory deduplication.
Setting the dump boolean option to off excludes the memory from
core dumps. This feature is also known as MADV_DONTDUMP.
The prealloc boolean option enables memory preallocation.
The host-nodes option binds the memory range to a list of NUMA
host nodes.
The policy option sets the NUMA policy to one of the following
values:
default
default host policy
preferred
prefer the given host node list for allocation
bind
restrict memory allocation to the given host node list
interleave
interleave memory allocations across the given host node
list
The align option specifies the base address alignment when QEMU
mmap(2) mem-path, and accepts common suffixes, eg 2M. Some
backend store specified by mem-path requires an alignment
different than the default one used by QEMU, eg the device DAX
/dev/dax0.0 requires 2M alignment rather than 4K. In such
cases, users can specify the required alignment via this
option.
-object
memory-backend-ram,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-
nodes,policy=default|preferred|bind|interleave
Creates a memory backend object, which can be used to back the
guest RAM. Memory backend objects offer more control than the
-m option that is traditionally used to define guest RAM.
Please refer to memory-backend-file for a description of the
options.
-object
memory-backend-memfd,id=id,merge=on|off,dump=on|off,prealloc=on|off,size=size,host-nodes=host-
nodes,policy=default|preferred|bind|interleave,seal=on|off,hugetlb=on|off,hugetlbsize=size
Creates an anonymous memory file backend object, which allows
QEMU to share the memory with an external process (e.g. when
using vhost-user). The memory is allocated with memfd and
optional sealing. (Linux only)
The seal option creates a sealed-file, that will block further
resizing the memory ('on' by default).
The hugetlb option specify the file to be created resides in
the hugetlbfs filesystem (since Linux 4.14). Used in
conjunction with the hugetlb option, the hugetlbsize option
specify the hugetlb page size on systems that support multiple
hugetlb page sizes (it must be a power of 2 value supported by
the system).
In some versions of Linux, the hugetlb option is incompatible
with the seal option (requires at least Linux 4.16).
Please refer to memory-backend-file for a description of the
other options.
-object rng-random,id=id,filename=/dev/random
Creates a random number generator backend which obtains entropy
from a device on the host. The id parameter is a unique ID that
will be used to reference this entropy backend from the virtio-
rng device. The filename parameter specifies which file to
obtain entropy from and if omitted defaults to /dev/random.
-object rng-egd,id=id,chardev=chardevid
Creates a random number generator backend which obtains entropy
from an external daemon running on the host. The id parameter
is a unique ID that will be used to reference this entropy
backend from the virtio-rng device. The chardev parameter is
the unique ID of a character device backend that provides the
connection to the RNG daemon.
-object
tls-creds-anon,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off
Creates a TLS anonymous credentials object, which can be used
to provide TLS support on network backends. The id parameter is
a unique ID which network backends will use to access the
credentials. The endpoint is either server or client depending
on whether the QEMU network backend that uses the credentials
will be acting as a client or as a server. If verify-peer is
enabled (the default) then once the handshake is completed, the
peer credentials will be verified, though this is a no-op for
anonymous credentials.
The dir parameter tells QEMU where to find the credential
files. For server endpoints, this directory may contain a file
dh-params.pem providing diffie-hellman parameters to use for
the TLS server. If the file is missing, QEMU will generate a
set of DH parameters at startup. This is a computationally
expensive operation that consumes random pool entropy, so it is
recommended that a persistent set of parameters be generated
upfront and saved.
-object
tls-creds-x509,id=id,endpoint=endpoint,dir=/path/to/cred/dir,priority=priority,verify-peer=on|off,passwordid=id
Creates a TLS anonymous credentials object, which can be used
to provide TLS support on network backends. The id parameter is
a unique ID which network backends will use to access the
credentials. The endpoint is either server or client depending
on whether the QEMU network backend that uses the credentials
will be acting as a client or as a server. If verify-peer is
enabled (the default) then once the handshake is completed, the
peer credentials will be verified. With x509 certificates, this
implies that the clients must be provided with valid client
certificates too.
The dir parameter tells QEMU where to find the credential
files. For server endpoints, this directory may contain a file
dh-params.pem providing diffie-hellman parameters to use for
the TLS server. If the file is missing, QEMU will generate a
set of DH parameters at startup. This is a computationally
expensive operation that consumes random pool entropy, so it is
recommended that a persistent set of parameters be generated
upfront and saved.
For x509 certificate credentials the directory will contain
further files providing the x509 certificates. The certificates
must be stored in PEM format, in filenames ca-cert.pem,
ca-crl.pem (optional), server-cert.pem (only servers),
server-key.pem (only servers), client-cert.pem (only clients),
and client-key.pem (only clients).
For the server-key.pem and client-key.pem files which contain
sensitive private keys, it is possible to use an encrypted
version by providing the passwordid parameter. This provides
the ID of a previously created "secret" object containing the
password for decryption.
The priority parameter allows to override the global default
priority used by gnutls. This can be useful if the system
administrator needs to use a weaker set of crypto priorities
for QEMU without potentially forcing the weakness onto all
applications. Or conversely if one wants wants a stronger
default for QEMU than for all other applications, they can do
this through this parameter. Its format is a gnutls priority
string as described at
<https://gnutls.org/manual/html_node/Priority-Strings.html>.
-object
filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off]
Interval t can't be 0, this filter batches the packet delivery:
all packets arriving in a given interval on netdev netdevid are
delayed until the end of the interval. Interval is in
microseconds. status is optional that indicate whether the
netfilter is on (enabled) or off (disabled), the default status
for netfilter will be 'on'.
queue all|rx|tx is an option that can be applied to any
netfilter.
all: the filter is attached both to the receive and the
transmit queue of the netdev (default).
rx: the filter is attached to the receive queue of the netdev,
where it will receive packets sent to the netdev.
tx: the filter is attached to the transmit queue of the netdev,
where it will receive packets sent by the netdev.
-object
filter-mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support]
filter-mirror on netdev netdevid,mirror net packet to
chardevchardevid, if it has the vnet_hdr_support flag, filter-
mirror will mirror packet with vnet_hdr_len.
-object
filter-redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support]
filter-redirector on netdev netdevid,redirect filter's net
packet to chardev chardevid,and redirect indev's packet to
filter.if it has the vnet_hdr_support flag, filter-redirector
will redirect packet with vnet_hdr_len. Create a filter-
redirector we need to differ outdev id from indev id, id can
not be the same. we can just use indev or outdev, but at least
one of indev or outdev need to be specified.
-object
filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_support]
Filter-rewriter is a part of COLO project.It will rewrite tcp
packet to secondary from primary to keep secondary tcp
connection,and rewrite tcp packet to primary from secondary
make tcp packet can be handled by client.if it has the
vnet_hdr_support flag, we can parse packet with vnet header.
usage: colo secondary: -object
filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object
filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 -object
filter-rewriter,id=rew0,netdev=hn0,queue=all
-object filter-dump,id=id,netdev=dev[,file=filename][,maxlen=len]
Dump the network traffic on netdev dev to the file specified by
filename. At most len bytes (64k by default) per packet are
stored. The file format is libpcap, so it can be analyzed with
tools such as tcpdump or Wireshark.
-object
colo-compare,id=id,primary_in=chardevid,secondary_in=chardevid,outdev=chardevid[,vnet_hdr_support]
Colo-compare gets packet from primary_inchardevid and
secondary_inchardevid, than compare primary packet with
secondary packet. If the packets are same, we will output
primary packet to outdevchardevid, else we will notify colo-
frame do checkpoint and send primary packet to outdevchardevid.
if it has the vnet_hdr_support flag, colo compare will
send/recv packet with vnet_hdr_len.
we must use it with the help of filter-mirror and filter-
redirector.
primary:
-netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
-device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=mirror0,host=3.3.3.3,port=9003,server,nowait
-chardev socket,id=compare1,host=3.3.3.3,port=9004,server,nowait
-chardev socket,id=compare0,host=3.3.3.3,port=9001,server,nowait
-chardev socket,id=compare0-0,host=3.3.3.3,port=9001
-chardev socket,id=compare_out,host=3.3.3.3,port=9005,server,nowait
-chardev socket,id=compare_out0,host=3.3.3.3,port=9005
-object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
-object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
-object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0
secondary:
-netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
-device e1000,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=red0,host=3.3.3.3,port=9003
-chardev socket,id=red1,host=3.3.3.3,port=9004
-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
If you want to know the detail of above command line, you can
read the colo-compare git log.
-object cryptodev-backend-builtin,id=id[,queues=queues]
Creates a cryptodev backend which executes crypto opreation
from the QEMU cipher APIS. The id parameter is a unique ID that
will be used to reference this cryptodev backend from the
virtio-crypto device. The queues parameter is optional, which
specify the queue number of cryptodev backend, the default of
queues is 1.
# qemu-system-x86_64 \
[...] \
-object cryptodev-backend-builtin,id=cryptodev0 \
-device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
[...]
-object
cryptodev-vhost-user,id=id,chardev=chardevid[,queues=queues]
Creates a vhost-user cryptodev backend, backed by a chardev
chardevid. The id parameter is a unique ID that will be used
to reference this cryptodev backend from the virtio-crypto
device. The chardev should be a unix domain socket backed one.
The vhost-user uses a specifically defined protocol to pass
vhost ioctl replacement messages to an application on the other
end of the socket. The queues parameter is optional, which
specify the queue number of cryptodev backend for multiqueue
vhost-user, the default of queues is 1.
# qemu-system-x86_64 \
[...] \
-chardev socket,id=chardev0,path=/path/to/socket \
-object cryptodev-vhost-user,id=cryptodev0,chardev=chardev0 \
-device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
[...]
-object
secret,id=id,data=string,format=raw|base64[,keyid=secretid,iv=string]
-object
secret,id=id,file=filename,format=raw|base64[,keyid=secretid,iv=string]
Defines a secret to store a password, encryption key, or some
other sensitive data. The sensitive data can either be passed
directly via the data parameter, or indirectly via the file
parameter. Using the data parameter is insecure unless the
sensitive data is encrypted.
The sensitive data can be provided in raw format (the default),
or base64. When encoded as JSON, the raw format only supports
valid UTF-8 characters, so base64 is recommended for sending
binary data. QEMU will convert from which ever format is
provided to the format it needs internally. eg, an RBD password
can be provided in raw format, even though it will be base64
encoded when passed onto the RBD sever.
For added protection, it is possible to encrypt the data
associated with a secret using the AES-256-CBC cipher. Use of
encryption is indicated by providing the keyid and iv
parameters. The keyid parameter provides the ID of a previously
defined secret that contains the AES-256 decryption key. This
key should be 32-bytes long and be base64 encoded. The iv
parameter provides the random initialization vector used for
encryption of this particular secret and should be a base64
encrypted string of the 16-byte IV.
The simplest (insecure) usage is to provide the secret inline
# $QEMU -object secret,id=sec0,data=letmein,format=raw
The simplest secure usage is to provide the secret via a file
# printf "letmein" > mypasswd.txt # $QEMU -object
secret,id=sec0,file=mypasswd.txt,format=raw
For greater security, AES-256-CBC should be used. To illustrate
usage, consider the openssl command line tool which can encrypt
the data. Note that when encrypting, the plaintext must be
padded to the cipher block size (32 bytes) using the standard
PKCS#5/6 compatible padding algorithm.
First a master key needs to be created in base64 encoding:
# openssl rand -base64 32 > key.b64
# KEY=$(base64 -d key.b64 | hexdump -v -e '/1 "%02X"')
Each secret to be encrypted needs to have a random
initialization vector generated. These do not need to be kept
secret
# openssl rand -base64 16 > iv.b64
# IV=$(base64 -d iv.b64 | hexdump -v -e '/1 "%02X"')
The secret to be defined can now be encrypted, in this case
we're telling openssl to base64 encode the result, but it could
be left as raw bytes if desired.
# SECRET=$(printf "letmein" |
openssl enc -aes-256-cbc -a -K $KEY -iv $IV)
When launching QEMU, create a master secret pointing to
"key.b64" and specify that to be used to decrypt the user
password. Pass the contents of "iv.b64" to the second secret
# $QEMU \
-object secret,id=secmaster0,format=base64,file=key.b64 \
-object secret,id=sec0,keyid=secmaster0,format=base64,\
data=$SECRET,iv=$(<iv.b64)
-object
sev-guest,id=id,cbitpos=cbitpos,reduced-phys-bits=val,[sev-device=string,policy=policy,handle=handle,dh-cert-file=file,session-file=file]
Create a Secure Encrypted Virtualization (SEV) guest object,
which can be used to provide the guest memory encryption
support on AMD processors.
When memory encryption is enabled, one of the physical address
bit (aka the C-bit) is utilized to mark if a memory page is
protected. The cbitpos is used to provide the C-bit position.
The C-bit position is Host family dependent hence user must
provide this value. On EPYC, the value should be 47.
When memory encryption is enabled, we loose certain bits in
physical address space. The reduced-phys-bits is used to
provide the number of bits we loose in physical address space.
Similar to C-bit, the value is Host family dependent. On EPYC,
the value should be 5.
The sev-device provides the device file to use for
communicating with the SEV firmware running inside AMD Secure
Processor. The default device is '/dev/sev'. If hardware
supports memory encryption then /dev/sev devices are created by
CCP driver.
The policy provides the guest policy to be enforced by the SEV
firmware and restrict what configuration and operational
commands can be performed on this guest by the hypervisor. The
policy should be provided by the guest owner and is bound to
the guest and cannot be changed throughout the lifetime of the
guest. The default is 0.
If guest policy allows sharing the key with another SEV guest
then handle can be use to provide handle of the guest from
which to share the key.
The dh-cert-file and session-file provides the guest owner's
Public Diffie-Hillman key defined in SEV spec. The PDH and
session parameters are used for establishing a cryptographic
session with the guest owner to negotiate keys used for
attestation. The file must be encoded in base64.
e.g to launch a SEV guest
# $QEMU \
......
-object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=5 \
-machine ...,memory-encryption=sev0
.....
During the graphical emulation, you can use special key combinations to
change modes. The default key mappings are shown below, but if you use
"-alt-grab" then the modifier is Ctrl-Alt-Shift (instead of Ctrl-Alt)
and if you use "-ctrl-grab" then the modifier is the right Ctrl key
(instead of Ctrl-Alt):
Ctrl-Alt-f
Toggle full screen
Ctrl-Alt-+
Enlarge the screen
Ctrl-Alt--
Shrink the screen
Ctrl-Alt-u
Restore the screen's un-scaled dimensions
Ctrl-Alt-n
Switch to virtual console 'n'. Standard console mappings are:
1 Target system display
2 Monitor
3 Serial port
Ctrl-Alt
Toggle mouse and keyboard grab.
In the virtual consoles, you can use Ctrl-Up, Ctrl-Down, Ctrl-PageUp
and Ctrl-PageDown to move in the back log.
During emulation, if you are using a character backend multiplexer
(which is the default if you are using -nographic) then several
commands are available via an escape sequence. These key sequences all
start with an escape character, which is Ctrl-a by default, but can be
changed with -echr. The list below assumes you're using the default.
Ctrl-a h
Print this help
Ctrl-a x
Exit emulator
Ctrl-a s
Save disk data back to file (if -snapshot)
Ctrl-a t
Toggle console timestamps
Ctrl-a b
Send break (magic sysrq in Linux)
Ctrl-a c
Rotate between the frontends connected to the multiplexer (usually
this switches between the monitor and the console)
Ctrl-a Ctrl-a
Send the escape character to the frontend
The following options are specific to the PowerPC emulation:
-g WxH[xDEPTH]
Set the initial VGA graphic mode. The default is 800x600x32.
-prom-env string
Set OpenBIOS variables in NVRAM, for example:
qemu-system-ppc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=hd:2,\yaboot' \
-prom-env 'boot-args=conf=hd:2,\yaboot.conf'
These variables are not used by Open Hack'Ware.
The following options are specific to the Sparc32 emulation:
-g WxHx[xDEPTH]
Set the initial graphics mode. For TCX, the default is 1024x768x8
with the option of 1024x768x24. For cgthree, the default is
1024x768x8 with the option of 1152x900x8 for people who wish to use
OBP.
-prom-env string
Set OpenBIOS variables in NVRAM, for example:
qemu-system-sparc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
-M [SS-4|SS-5|SS-10|SS-20|SS-600MP|LX|Voyager|SPARCClassic]
[|SPARCbook]
Set the emulated machine type. Default is SS-5.
The following options are specific to the Sparc64 emulation:
-prom-env string
Set OpenBIOS variables in NVRAM, for example:
qemu-system-sparc64 -prom-env 'auto-boot?=false'
-M [sun4u|sun4v|niagara]
Set the emulated machine type. The default is sun4u.
The following options are specific to the ARM emulation:
-semihosting
Enable semihosting syscall emulation.
On ARM this implements the "Angel" interface.
Note that this allows guest direct access to the host filesystem,
so should only be used with trusted guest OS.
The following options are specific to the ColdFire emulation:
-semihosting
Enable semihosting syscall emulation.
On M68K this implements the "ColdFire GDB" interface used by
libgloss.
Note that this allows guest direct access to the host filesystem,
so should only be used with trusted guest OS.
The following options are specific to the Xtensa emulation:
-semihosting
Enable semihosting syscall emulation.
Xtensa semihosting provides basic file IO calls, such as
open/read/write/seek/select. Tensilica baremetal libc for ISS and
linux platform "sim" use this interface.
Note that this allows guest direct access to the host filesystem,
so should only be used with trusted guest OS.
NOTES
In addition to using normal file images for the emulated storage
devices, QEMU can also use networked resources such as iSCSI devices.
These are specified using a special URL syntax.
iSCSI
iSCSI support allows QEMU to access iSCSI resources directly and
use as images for the guest storage. Both disk and cdrom images are
supported.
Syntax for specifying iSCSI LUNs is
"iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>"
By default qemu will use the iSCSI initiator-name
'iqn.2008-11.org.linux-kvm[:<name>]' but this can also be set from
the command line or a configuration file.
Since version Qemu 2.4 it is possible to specify a iSCSI request
timeout to detect stalled requests and force a reestablishment of
the session. The timeout is specified in seconds. The default is 0
which means no timeout. Libiscsi 1.15.0 or greater is required for
this feature.
Example (without authentication):
qemu-system-i386 -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
-cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
-drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via URL):
qemu-system-i386 -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via environment variables):
LIBISCSI_CHAP_USERNAME="user" \
LIBISCSI_CHAP_PASSWORD="password" \
qemu-system-i386 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
NBD QEMU supports NBD (Network Block Devices) both using TCP protocol
as well as Unix Domain Sockets.
Syntax for specifying a NBD device using TCP
"nbd:<server-ip>:<port>[:exportname=<export>]"
Syntax for specifying a NBD device using Unix Domain Sockets
"nbd:unix:<domain-socket>[:exportname=<export>]"
Example for TCP
qemu-system-i386 --drive file=nbd:192.0.2.1:30000
Example for Unix Domain Sockets
qemu-system-i386 --drive file=nbd:unix:/tmp/nbd-socket
SSH QEMU supports SSH (Secure Shell) access to remote disks.
Examples:
qemu-system-i386 -drive file=ssh://user@host/path/to/disk.img
qemu-system-i386 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img
Currently authentication must be done using ssh-agent. Other
authentication methods may be supported in future.
Sheepdog
Sheepdog is a distributed storage system for QEMU. QEMU supports
using either local sheepdog devices or remote networked devices.
Syntax for specifying a sheepdog device
sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag]
Example
qemu-system-i386 --drive file=sheepdog://192.0.2.1:30000/MyVirtualMachine
See also <https://sheepdog.github.io/sheepdog/>.
GlusterFS
GlusterFS is a user space distributed file system. QEMU supports
the use of GlusterFS volumes for hosting VM disk images using TCP,
Unix Domain Sockets and RDMA transport protocols.
Syntax for specifying a VM disk image on GlusterFS volume is
URI:
gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...]
JSON:
'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...",
"server":[{"type":"tcp","host":"...","port":"..."},
{"type":"unix","socket":"..."}]}}'
Example
URI:
qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img,
file.debug=9,file.logfile=/var/log/qemu-gluster.log
JSON:
qemu-system-x86_64 'json:{"driver":"qcow2",
"file":{"driver":"gluster",
"volume":"testvol","path":"a.img",
"debug":9,"logfile":"/var/log/qemu-gluster.log",
"server":[{"type":"tcp","host":"1.2.3.4","port":24007},
{"type":"unix","socket":"/var/run/glusterd.socket"}]}}'
qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
file.debug=9,file.logfile=/var/log/qemu-gluster.log,
file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket
See also <http://www.gluster.org>.
HTTP/HTTPS/FTP/FTPS
QEMU supports read-only access to files accessed over http(s) and
ftp(s).
Syntax using a single filename:
<protocol>://[<username>[:<password>]@]<host>/<path>
where:
protocol
'http', 'https', 'ftp', or 'ftps'.
username
Optional username for authentication to the remote server.
password
Optional password for authentication to the remote server.
host
Address of the remote server.
path
Path on the remote server, including any query string.
The following options are also supported:
url The full URL when passing options to the driver explicitly.
readahead
The amount of data to read ahead with each range request to the
remote server. This value may optionally have the suffix 'T',
'G', 'M', 'K', 'k' or 'b'. If it does not have a suffix, it
will be assumed to be in bytes. The value must be a multiple of
512 bytes. It defaults to 256k.
sslverify
Whether to verify the remote server's certificate when
connecting over SSL. It can have the value 'on' or 'off'. It
defaults to 'on'.
cookie
Send this cookie (it can also be a list of cookies separated by
';') with each outgoing request. Only supported when using
protocols such as HTTP which support cookies, otherwise
ignored.
timeout
Set the timeout in seconds of the CURL connection. This timeout
is the time that CURL waits for a response from the remote
server to get the size of the image to be downloaded. If not
set, the default timeout of 5 seconds is used.
Note that when passing options to qemu explicitly, driver is the
value of <protocol>.
Example: boot from a remote Fedora 20 live ISO image
qemu-system-x86_64 --drive media=cdrom,file=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
qemu-system-x86_64 --drive media=cdrom,file.driver=http,file.url=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
Example: boot from a remote Fedora 20 cloud image using a local
overlay for writes, copy-on-read, and a readahead of 64k
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"https://dl.fedoraproject.org/pub/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2
qemu-system-x86_64 -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on
Example: boot from an image stored on a VMware vSphere server with
a self-signed certificate using a local overlay for writes, a
readahead of 64k and a timeout of 10 seconds.
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2
qemu-system-x86_64 -drive file=/tmp/test.qcow2
SEE ALSO
The HTML documentation of QEMU for more precise information and Linux
user mode emulator invocation.
AUTHOR
Fabrice Bellard
2018-06-01 QEMU.1(1)